[Update 12:47 pm] According to Maureen Mullen at CSNNE.com, Middlebrooks is "on his way" to Boston from Toledo, although it hasn't been determined yet if he is being promoted, or being held in reserve. The Red Sox await more on the condition of Youkilis' back.
According to Alex Speier, if Kevin Youkilis once again is a scratch for tonight's game against Brandon McCarthy and the Oakland Athletics, then it will be top prospect Will Middlebrooks getting the call to the majors today, not starting pitching project Aaron Cook.
Middlebrooks missed Monday's contest due to a thumb problem, but was deemed healthy and returned to play Tuesday evening. Because Middlebrooks' status was unclear, it was Jose Iglesias who was called up, a move that in turn made it seem as if Youkilis might not be so injured that a clear replacement was needed.
The Red Sox made it clear that they don't want to interrupt Middlebrooks' development at Triple-A to replace Youkilis this early in the year unless it was a situation in which Youkilis was injured. As he's missed three-straight games, and couldn't loosen up enough to pinch-hit in the ninth inning on Tuesday (or wasn't healthy enough to be used as anything but a decoy in the on-deck circle), it's safe to say he's not feeling his best.
While Middlebrooks struggled closing out the 2011 season at Triple-A -- the first time in his professional career he spent time at two different levels in the same campaign -- he's more than rebounded in his first 100 plate appearances of 2012. He's hitting .333/.380/.677 with nine homers and 13 extra-base hits overall, and after punching out in 30 percent of his plate appearances at the level (and 24 percent at Double-A), he's whiffing just 18 percent of the time. Add to that a slight bump in his walk rate, and a noticeable improvement in his plate discipline, and it looks like Middlebrooks is making his second significant jump in results.
If Middlebrooks does get the call-up, it doesn't mean the Sox aren't going to ever call up Cook. They have 48 hours to do so after Cook exercises his opt-out clause, and Cook has 24 hours (starting at 12:01 am Wednesday) to invoke that. It's likely Iglesias would be sent back down for Cook, should Middlebrooks take the currently-empty roster spot left by Lars Anderson's departure.