Matt Moore: One of the hottest pitchers in the minor leagues, I don't see what else Moore has to prove at single-A. He's thrown strikes much more consistently, and has walked 23 batters in his last 62 2/3 innings (3.3 per 9) as compared to 31 batters in his first 48 1/3 (5.7 per 9). He's second in the minors in strikeouts with 153, and is striking out over 12 per 9 innings.
The Rays are generally cautious in terms of promotions, but there is some precedent here. Back in 2007, Wade Davis and Jake McGee were teaming up to dominate the Florida State League with Vero Beach. Davis was promoted around mid-season, while McGee got the bump about 3/4 of the way through. Moore compares favorably to McGee, with better strikeout numbers (though worse control) and a more well-rounded arsenal, as McGee was mostly blowing hitters away with his fastball. In fact, the Rays could open up a spot in Montgomery's rotation for Moore by promoting...
Jake McGee: Like Moore, McGee has overcome a slow start to look like his old dominating self. He's striking out well over a batter per inning (91 in 76 2/3) and has his fastball back into the 94-95 mph range. His last start was on July 22 and was a bit of a bump in the road, with 6 earned runs allowed. Assuming that he was held out of his most recent would-be start to control his innings and not because of some injury, a promotion into the Durham bullpen would make sense.
McGee threw 140 innings in 2007, then 77 2/3 before injuring his elbow in 2008. Coming back from surgery, he pitched 30 innings last season and is at 76 2/3 this year. A month and change with the Bulls, who appear headed for a playoff spot, would mean roughly 15-18 innings, putting him just under 100 for the season, a reasonable number. If McGee really shined out of the bullpen and his arm stayed fresh, then a September call-up wouldn't be out of the question. Additionally, it would prep McGee for a bullpen role next season, since the big-league rotation is backed up as it is.
Nick Barnese: Back to Charlotte's rotation for this one. Barnese hasn't quite been at the level of 2007 Wade Davis, but he's been plenty good. In last nine starts, he's walked just 8 hitters, and has walked 22 on the season, a 1.77/9 rate, and his 7.49 K/9 is solid. His stuff doesn't match Moore or McGee's, but he's arguably been the most consistent pitcher in the Rays system this year. Additionally, Barnese and Moore are both 21 years old, and while that's not necessarily "old" for the Florida State League, they are both good enough to be challenged at AA.