Cody Kukuk, LHP
Kukuk had the kind of season you would expect from a 20-year-old left-hander with control problems back in 2013, as he walked nearly seven batters per nine. At the same time, he also showed plenty of swing-and-miss, punching out 9.5 batters per nine while limiting hits and homers. While his walk rate improved as the season went on, with Kukuk producing a 60/29 strikeout-to-walk ratio and 4.8 per nine walk rate during the last two months of the year, he still had enough to learn at Low-A that the Red Sox had him repeat the level.
The decision to hold him back appears to be paying off in the early going, as the 21-year-old southpaw has struck out 17 batters in his first three starts and 13 innings, against seven walks while allowing just four runs. Kukuk's ceiling isn't as high as Henry Owens, a lefty who put up similar numbers at a similar age in the low minors, but there is talent here, and both Kukuk and the Red Sox have some time to let it show itself. If he begins to dominate, maybe he gets a bump to High-A Salem mid-season, but let's wait until he's got some innings behind him before assuming as much.
Tzu-Wei Lin, SS
Lin didn't show much with the bat in his debut at short-season Lowell in 2013, but that wasn't a surprise considering he was a light-hitting shortstop in his age-19 campaign. His glove is the focus here -- sound familiar, Red Sox fans? -- but there is some hope that eventually, his bat will be good enough to be inserted into a big-league lineup so that he's not all glove. He's off to a good start in that regard in 2014, batting .289/.370/.340 with a pair of steals and six walks against eight strikeouts.
Don't expect Lin to ever hit for power, but making contact and drawing walks is a definite possibility. If he can stick around this 700 OPS level for much of the year, it'll be a good sign for his future. Remember, though, that pitchers get better the higher up the organizational ladder you move, so success in Low-A doesn't answer all of the questions about Lin in the same way a couple of solid weeks doesn't tell us how his entire 2014 will go.
Carlos Asuaje, 2B
Asuaje was Boston's 11th-round selection in the 2013 draft, but there is reason to believe he might actually have a big-league future despite this. He was the 208th-ranked prospect on the draft board for Baseball America, a better ranking than you might expect for an 11th-rounder:
Asuaje offers similarities to Cardinals farmhand Kolten Wong, both with his size (5-foot-9, 165 pounds) and solid line-drive stroke. He's not as powerful as Wong so doesn't have as much offensive value, but he has gap power and average speed that plays up thanks to his good baserunning instincts.
A line-drive hitter who can control the strike zone, draw walks, and is a quality baserunner can have a career, even if they don't have much in the way of power. He's actually shown some pop to start with, hitting four doubles in his first 10 games with the Drive, but don't expect him to go all Mookie Betts on us just because he's also tiny and plays second. Asuaje is 22, in Low-A, and played college ball, so success at this level is something we should expect. The real test for him will come later on in his career, but seeing him hit the ground running is still a good thing.