The 31 year-old 5'11" lefty was signed by the Astros in 1999, and made his debut in 2005. He improved every year, and last year he seemed to put it all together, throwing 200+ innings for the first time in his career. He won 14 games and had a 3.02 ERA, 1.24 WHIP. People were expecting him to take another giant step forward this year, but he got off to a terrible start before rebounding recently. For his career, he's 60-63 with a 4.31 ERA and 1.37 WHIP. He's made 5 starts versus the Mets, and is 2-2 with a 3.68 ERA. He was 0-1 in his only start versus the Mets last year (6 innings, 8 hits, 1 walk, 3 earned runs).
Wandy is a three-pitch pitcher who changes arm angles (overhand to low 3/4s) as well as speeds, with a fastball that averages 90 mph, a tight 12-6 curveball (75 mph), and a change-up (84 mph). This season he has started to throw a lot more two-seam fastballs (so technically a fourth pitch), so he's getting more ground-balls, but his swinging strike % and K rate is down significantly (8.2 from 9.2, and 7.3 from 8.5 K/9 last year). He uses his curve-ball as his strike out pitch, but it hasn't been effective this year (decreased ability to throw it for a strike from last year, but he's still above league average at 62%). He has thrown less strikes this year, only 45%, when his career average is 51%.
This year he started out terribly, and his record stood at 3-10 after 14 starts, and an ERA over 6. But since then, he has run off 8 of 9 quality starts, improving his record to 9-11, and his ERA is now 4.18, and is FIP 3.66. In his last start versus the Braves, he let up only 1 earned run (2 runs) in 7 innings, scattering 5 hits, walking 1 and striking out 9. In his last 4 starts (28 1/3 innings), he has allowed only 2 earned runs and 23 base-runners (19 hits, 4 walks = very impressive).
He's currently arbitration eligible and making 5 million this season; there were some whispers he was on the trading block, but I doubt that now since he has turned his season around unless the Astros don't want to pay him next year. He is a low #2- very good #3 starter.