Starting with the lone member of the Tigers that has gotten a few starts for Mesa, RHP Tommy Collier has had a very successful fall showing, yielding just one run in four games (three starts), good for a miniscule 0.64 ERA. He's also struck out ten and walked just two, showing signs of regained command that was lacking this season.
Collier headed to the AFL after he missed nearly half the season with a groin injury, and the Tigers wanted him to get more work in for the season.
As mentioned, his performance has been stellar, and his command has been good. However, velocity has been a concern for him. A pitcher that joined the organization sitting 91-92, topping out at 93, is now sitting 87-88 and barely touching 90. A 3-4 MPH velo drop for someone that wasn't a flame thrower to begin with can be a large concern.
The only other Tiger that has gotten a start for the Solar Sox has been left hander Blaine Hardy. The Tigers signed Hardy in late April and sent him to Erie, and then transferred him to Toledo in June, where they tried him in the rotation with some rather impressive success.
Hardy thus far has been solid though not spectacular in the AFL but improving as the season has gone on, posting a 4.50 ERA over seven appearances, including one start. He's striking out more than a batter per inning, and has struck out seven over his last two appearances, spanning five innings.
Dating back to the end of the year in Toledo, he's made impressive strides with his breaking ball as he was stretched out. At 26, he's not prime age for being a prospect, but could be looked at next spring as a potential option in the Tigers bullpen with a decent enough fastball (around 90 MPH), a solid change and the emerging breaking ball.
Moving to other relievers, arguably no member of the 2013 draft class had a more impressive start to their pro career than right hander Corey Knebel, who posted a miniscule 0.87 ERA over 31 games in West Michigan, including striking out nearly 12 batters per nine. He hasn't been able to match that success in the AFL, with a 4.70 ERA over eight games, including nine strikeouts and three walks.
Scouting reports are mixed on Knebel's AFL showing – he has a power fastball and a potentially devastating breaking pitch. But at times he still spins the pitch (leading some scouts to believe he has both a curve and a slider), and his mechanics don't scream repeatability.
Scout.com national baseball analyst Kiley McDaniel pegged his fastball as a potential 70-grade pitch, and despite the inconsistency, the breaking pitch as 65-grade, so the potential is still clearly there. His season also started back in February with the Longhorns, meaning he's been pitching off-and-on for the last ten months, and may have simply tired at the end of a long season.
The Tigers have no plans at the moment to try and stretch Knebel out into a starter. If he shows up this spring fresh and with a snappy breaking pitch, he's a likely candidate to be pushed aggressively in potential hopes he can be in Detroit in the summer – the decision to push Knebel to the AFL was very deliberate in that sense.
Finally, Kenny Faulk has been getting some work in this fall in Mesa, and of the group, likely has hurt his stock the most. After a solid showing in Toledo, Faulk was hoping to use the AFL to position himself as a candidate for the Tigers bullpen in 2014. But his ERA is approaching eight at 7.71, and his consistency has been all over the map.
Most concerning arguably has been his strikeout-to-walk ratio, that sits at a discouraging 1.1. In his most recent outing on November 8, he tossed 1 2/3 scoreless innings, but walked three in the process. Pitchers can occasionally be wildly effective, but it's not a long-term strategy for success, especially when looking at the possibility of facing big league hitters next year.