UPDATE: Turner will be making the start tonight for Detroit, and according to Danny Knobler, this start is not a showcase, and they do not intend to trade him.
According to Jon Heyman, the Tigers will be calling up top prospect Jacob Turner tomorrow. Turner had been rumored to be a key piece in the Tigers' attempt to acquire Ubaldo Jimenez, but it appears that the Tigers are no longer in the running for his services, per Danny Knobler. Turner was on the 40-man roster already, but they will need to clear a spot for him on the 25-man.
Turner was the #1 prospect in the Tigers' system on most lists coming into the season, and had been the team's top draft pick back in the 2009 draft. Turner came into the season as Baseball America's #21 prospect in all of baseball, and spent the entirety of the 2011 season with their AA affiliate, Erie.
Turner has a 3-5 record this year, with a 3.48 ERA and 90 strikeouts in 113 2/3 innings pitched. Minor League Ball's John Sickels gave Turner an A- grade (borderline B+) in the offseason, and worried that the Tigers might rush him. This really doesn't seem like that big of a surprise, as the Tigers have been known in the past for bringing their pitchers up quickly through their system (Rick Porcello, among others).
Turner turned 20 in May, and will be the first high school player from the 2009 draft to reach the big leagues. I imagine they are bringing him up to start tomorrow's game in place of Duane Below, but I haven't seen any confirmation on that yet. This could very well be a showcase, but I would imagine that any teams interested in Turner have already seen him pitch at least a few times in the past month.