Dustin Ackley and Jenrry Mejia impressive in AFL

While the postseason rolls on at the major league level, I was able to spend the past week at the Arizona Fall League getting a close look at some of the top prospects in the minor leagues.

The most impressive arm so far has been Jenrry Mejia of the New York Mets, who was on a short pitch count but showed two above-average pitches and a chance for a third. Mejia's fastball sat from 93-96 mph and touched 98, he also threw a plus changeup that looked more like a two-seamer at 85-87. It should be noted, though: the latter pitch was a little inconsistent. His curveball was even less consistent, but he threw one very sharp one for a called third strike at 78 mph, with good depth and clear two-plane break. He comes from a slot just below 3/4 and needs to focus on staying on top of the ball. He missed a chunk of the second half with a strained finger, which could impact how he grips the ball even now. He has a strong, thick build. The velocity comes easily, and if his command is better than what he showed on Wednesday and he can snap off that good curveball more frequently, he's a potential No. 1 or No. 2 starter.

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Dustin Ackley of the Seattle Mariners, the No. 2 overall pick in the 2009 MLB draft, is one of the most impressive hitters here. He's very short to the ball and has good bat control, taking a 94 mph fastball away from a lefty to left field for a line-drive single. Fellow Mariners farmhand Philippe Aumont threw a six-pitch inning with one non-fastball (a slurvy 78 mph curveball), but his fastballs were all 92-95 with good life.

Scott Mathieson of the Philadelphia Phillies hasn't pitched in the majors since 2006; he underwent Tommy John surgery at the end of that season and threw just eight innings total over the next two years. He's back now as a reliever and showed a nasty two-pitch mix -- a fastball at 93-97 mph and a hard slider at 82-86 mph. He pitches aggressively with his fastball and seems to have a lot of confidence in it. I imagine that if he'd been healthy all year, he would have ended up in the Phillies' major league 'pen and been considered for the playoff roster.

Five of the top ten picks in this year's draft are in the AFL -- including Ackley, Stephen Strasburg (who throws Friday night at Phoenix Municipal Stadium), Mike Minor, Mike Leake and Drew Storen. Storen was solid, throwing at 90-94 mph combined with an 82-86 mph slider with good tilt, although his command wasn't as otherworldly as it was in the spring and summer. Leake was his usual self, throwing five pitches (two- and four-seamers, slider, change, curveball and I may have even seen a cutter) for strikes and changing speeds constantly. His two-seamer and changeup were his best pitches, and his curveball, which had little or no depth, was his worst. Minor was the only disappointment, as he didn't have the good curveball I saw at the SEC tournament in May; he was 87-92, mostly 89-91, with an average changeup and fringy slider.

Domonic Brown -- yes, with two o's -- of the Phillies was a stumbling block in the defending champs' talks with Toronto for Roy Halladay, and given his tool set it's easy to see why. He's a superb athlete who can run and throw and has some raw power. That said, he's still pretty crude, succeeding on the basis of his ridiculous athletic ability. His reads in right field are really poor, although he's fast enough to catch up to balls he misreads off the bat, and while he has arm strength, his throwing motion needs work. He also leaks badly at the plate, but again, he's got the bat speed to compensate. He's still one of the top 20 or so prospects in the minors, but he still needs some polishing before he's ready to race to the majors.