Roy Halladay's velocity a concern

The New York Mets face the Philadelphia Phillies tonight (ESPN, 7 ET) with Roy Halladay getting the nod for Philadelphia. Roy Halladay Halladay

A key tonight will be Halladay's velocity, which has decreased significantly over the last several seasons. In 2010, Halladay's cutter averaged 91.3 miles per hour. This season, it has dipped to 88.9.

His sinker has also suffered the same fate. In 2009, his sinker averaged 92.6 mph and topped out at 95.8. In 2012, that average is at 90.6 with a max of 92.8.

No pitcher in baseball has thrown more innings than Halladay in the regular season since 2006, and he has the most complete games of any active pitcher, 16 more than the next-closest.

Most Innings Pitched - Regular Season Since 2006

Tonight's opponent has yet to solve Halladay, however. Since joining the Phillies in 2010, Halladay is 7-0 with a 1.68 ERA in seven starts against the Mets. He has posted a 1.66 ERA with 15 strikeouts and just one walk in three starts at Citi Field, and he didn’t allow a run in two of those starts. He has never allowed a home run to a current Mets batter.

Halladay is also 20-3 against the NL East since the Phillies acquired him with a 2.24 ERA and a K-to-BB ratio of 8.39.

His opponent tonight, Jonathon Niese, is off to a relatively strong start this season thanks to his opponents' batting average on balls in play. Last season it was .344, the highest in the majors. This year it's down to .250, lower than 97 other pitchers.

Niese is allowing runs mainly because he's having trouble keeping the ball in the ballpark. He has a groundball-to-flyball ratio of 1.10, the same as 2011, but last season only seven percent of fly balls he allowed were home runs. This season, that's up to 10.8 percent.

A key matchup tonight will be Niese against Placido Polanco, as Polanco is 10-24 (.417) against Niese.