The 6'6" 27-year old Hammel was drafted by the Rays in 2002, and made his debut in 2006. He was considered a super-two and lost out on the 5th starter job last spring training (and was out of options), hence the reason he was traded to the Rockies. He's 25-29 in his career, with a 4.98 ERA and 1.47 WHIP, but for the Rockies he's 18-14, with a 4.35 ERA and 1.35 WHIP. He has not faced the Mets in his career.
Hammel is a four-pitch pitcher, and he throws from a 3/4 arm slot. His location of his fastball has greatly improved, and he throws it between 90-94 (average 93). It does not have a lot of movement. His curveball is a plus pitch (77 mph) and he also throws a sweeping slider (84 mph). He sparingly uses his change-up (85 mph, 6% of his pitches). His two best pitches this year are his slider and curve. His curveball use increases with 2 strikes, but he's not afraid to throw his slider either in that situation.
This year Hammel has made strides to become more than a league average pitcher, as he's 8-6 with a 4.38 ERA and 1.29 WHIP. He missed some time earlier in the year with a groin injury. In May and early June he had a 6 start stretch that his stats were: 2.41 ERA, 1.07 WHIP, 7.7 K/9. He's striking out a career high 7.4 K/9, and walking a manageable 2.4 W/9. He could be better than his ERA indicates, as his FIP is 3.54. He's let up 3+ runs in his last five starts, but won his last game vs the Pirates (6 innings, 3 runs, only 5 base runners).
He's a solid #4/5 starter that is still learning how to pitch and gain confidence.