Your guide to new Red Sox starter Eduardo Rodriguez

At this time last year, the Red Sox didn't have anyone in their system with top-of-the-rotation potential. They had plenty of pitching prospects, and across all levels of their minor-league system, but none of them had that ceiling. That all changed at the July 31 trade deadline, however, when the Sox acquired lefty prospect Eduardo Rodriguez from the division-rival Orioles. He didn't automatically give them that kind of pitcher, but when you combine his past success and expectations with the way he arrived on the scene for the Double-A Sea Dogs, you could tell Boston suddenly had something different on their hands.

Now, Rodriguez is set to make his big-league debut on Thursday night against the Rangers. It's just a spot start, an artificial off-day for the starting five who will not see an actual one this week thanks to Monday's Memorial Day contests. It's also an audition for future work by Rodriguez, though, and an opportunity for Red Sox fans to catch a glimpse of the pitcher who will likely be a major part of the rotation by next season, if not sooner.

Before Rodriguez takes the mound, let's give y'all a rundown of just who he has been, who he is now, and who he's expected to be from here on out.

Rodriguez signs with the O's

Eduardo Rodriguez signed as an international free agent for $175,000 with Baltimore before the 2010 season. He was considered maybe a potential back-end starter at the time, so his performance in in the Dominican Summer League came as a surprise to the Orioles, according to Baseball America's report from the time: Rodriguez threw 65 innings as a 17-year-old with a 2.33 ERA and 2.2 times as many strikeouts as walks. That's good on its own, but some context helps it along: the average pitcher in the DOSL was 19, and the average batter 18.5. Rodriguez faced 263 batters all told in his pro debut, and only on 13 occasions were those hitters younger than he was.

In 2011, Rodriguez jumped to the rookie-level Gulf Coast League, where he was now more than 2.5 years younger than the average pitcher and two younger than the hitters he was facing. Once again, most of his competition were older opponents, and it didn't slow him one bit, as he struck out over nine batters per nine and posted a 1.81 ERA in his 48 frames. He made just one start in short-season ball before the campaign ended, and the next year, would take the leap to a full-season league.

Rodriguez becomes a legit prospect

Rodriguez's 2011 made him the 30th-ranked prospect in the Orioles' system, per Baseball America's reckoning. Not everyone was so low on him, however: Kevin Goldstein at Baseball Prospectus rated Rodriguez 11th in the organization, with the concerns at that time mostly the things that pitchers can't prove in short-season ball, such as if they can handle a starter's workload or if their secondaries are going to be assets or problems. Goldstein did mention that Rodriguez was praised for his feel for pitching, which was no small thing for someone as young as the southpaw.

The 2012 season is the one where more prospect analysts started to recognize what the Orioles might have in Rodriguez. Just 19, he pitched the entire season at Low-A for Delmarva in the Sally League, and while the numbers might not pop out at you, remember, he was 19. Rodriguez threw 107 innings, recorded a 3.70 ERA, and while he struck out just over six batters per nine, he maintained a 2.4 strikeout-to-walk ratio. He faced 454 batters, 426 of them older than he was.

Baseball America changed their tune on Rodriguez after the season, bumping him from number 30 to number five on the O's rankings, and jumped from the back-end starter rhetoric to the far more intriguing, "profiles as a mid-rotation starter, though some suggest he has an even higher ceiling." Baseball Prospectus, whose prospect department was in Jason Parks' hands at this time, bumped Rodriguez from 11 to four. The questions at this time had to do with Rodriguez's velocity -- it still was in the high-80s far too often -- and his ability to work deep into games. Because of this, he still profiled as a mid-rotation arm here, one who might end up being a five instead.

Still, this was all a significant jump thanks to Rodriguez's first year of full-season pitching, and there was more to come.

The O's challenge Rodriguez. Again.

The Orioles had already been pushing Rodriguez through the system quickly, but they stepped it up in 2013, first by bumping him to High-A as expected after his successful run in Low-A, and then by promoting the southpaw to Double-A. Rodriguez was 20 years old and in Double-A, and he succeeded: a 4.22 ERA doesn't jump off the page, but that's just one of the reasons you don't scout stats by themselves.

Here is a pitcher who was in Low-A -- and young for the level! -- a year prior to his promotion to Double-A in mid-2013. He struck out just under a batter per inning in his 60 innings at Double-A, didn't give up an excess of homers, and mostly kept his walks under control. The average pitcher in the Eastern League in 2013 was 24.6 years old, the average hitter, 24.4. Rodriguez faced 576 hitters older than he was over the course of the season, which also included a stop in the Arizona Fall League.

He didn't jump up the prospect rankings any further, thanks mostly to the Orioles' strong system: he sat third according to Baseball America, and fourth again for Baseball Prospectus. He was considered a number three starter by both outlets at this time, with BP stating that Rodriguez needed to repeat his motion more consistently in order to have the command required to be more than that in the majors, and BA also mentioned that his delivery, while making progress, was still a work in one.

So, Rodriguez was a legitimate pitching prospect, one who could be a mid-rotation arm. Scouts didn't believe he could be more than that, because he didn't have the obvious plus offering to go along with his fastball, the command of which was still a bit spotty because of his mechanics. No one said he wouldn't ever figure these things out, but as constructed at the time, these were the issues that would keep Rodriguez from being more than his projections suggested.

Rodriguez struggles and is traded

When Rodriguez didn't take any steps forward in his second go of things at Double-A, he became trade bait at the deadline for the O's. They shopped him around, and not just to the Red Sox, but it was Boston who convinced Baltimore to part with him by dangling free-agent-to-be Andrew Miller. At the time of the deal, Rodriguez had a 4.79 ERA for Double-A Bowie, with a lower strikeout rate than he did the year before. Things changed once he got to Boston's Double-A club, though, with Rodriguez finishing his year with six starts that resulted in almost five times as many strikeouts per nine and a 0.96 ERA.

It wasn't just the numbers that improved. Rodriguez, with some coaching from the Sox, had a more consistent delivery with more consistent fastball command at his disposal in those six starts. He used a different change-up than what he had utilized with the Orioles, and then used it in more situations -- specifically, against left-handed batters. He began to pitch down in the zone and to pitch inside more often, and it helped keep hitters off-balance and brought on more strikeouts for the southpaw.

Top-of-the-rotation potential

While Baseball Prospectus didn't change their view of Rodriguez, still expecting him to be a mid-rotation arm, Baseball America's reports became more breathless:

He shows impressive athleticism and a repeatable delivery. Rodriguez's explosive fastball and changeup after joining the Sox both graded as plus offerings. If his slider develops to at least average, his potential is immense. "That kid can be Johan Santana Part 2," one evaluator said. "If his breaking ball improves one tick, he's going to be outstanding."

"He could be Johan Santana!" is a far cry from "mid-rotation arm, " and someone saying it out loud doesn't mean you should expect Santana v2.0, not unless you love being disappointed. It is a reminder, though, that Rodriguez is still just 22, and in the last year, has made serious improvements. He entered 2015 already a better prospect than anyone had envisioned him to be back when he was signed an in his early years as a pro. His performance at Triple-A this season has justified the hype to an extent, too, as he looks like one of the best arms in the entire International League thanks to striking out 6.3 times as many batters as he's walked, with his command and stuff from his brief 2014 run with Boston's Double-A affiliate carrying over after his promotion.

Rodriguez as a top-of-the-rotation arm is still something of a dream -- even that optimistic evaluator above believes the lefty still needs to take a step forward to make his vision a reality, and part of the choice of Johan might just be because both are Venezuelan. (If there is something excited scouts love more than comps, it's comps of players from the same foreign country.) At the same time, maybe this scout just meant that Rodriguez, like Santana, was in line to pitch better than anyone ever imagined he would -- if you'll recall, Santana was selected in the Rule 5 draft by the Twins, and then became his generation's greatest pitcher.

Santana's reign began in 2003, when he was left in the Minnesota rotation for 14 eye-opening starts after his initial grooming in relief. That's a far more apt comparison for Rodriguez, in terms of continually impressing beyond what it's believed he would achieve, and at a young age each time. And hey, Rodriguez will be 23 next year.

So, be excited about Boston's lefty, who is the top pitching prospect in the entire system, likely big-league ready, and could very well be the top-of-the-rotation arm the Sox need -- not in 2015, not when he's still just 22 and only recently solved Triple-A, but someday. There is no one else with that potential in the organization, and even if Rodriguez is "only" a three or manages to pitch like a number two, that's still a massive achievement for a prospect who wasn't even ranked in the Orioles system after his impressive pro debut. Keep your excitement a bit in check, though, because even though Rodriguez has a history of exceeding expectations as well as one of growth where he most needs it, he's still a young pitcher.

There are no guarantees with prospects, even ones who have achieved so much relative to expectations as Rodriguez. His first start might not be a great one, and maybe his eventual second and third or however many might not be either, but if his past is any indication, he'll figure things out.