He has to have some of the most severe home vs. away splits in Major League history. 
Look at his career:
36-26 with a 3.43 ERA, 1.24 WHIP and with the league batting .240 against him in 88 career home starts
24-39 with a 5.12 ERA, 1.48 WHIP and the league hitting .285 off of him in 81 career road starts
Nobody knows why the disparity exists, as Minute Maid Park is not really a pitcher's park, but the disparity is real over a fairly nice sampling.
Look at his career:
36-26 with a 3.43 ERA, 1.24 WHIP and with the league batting .240 against him in 88 career home starts
24-39 with a 5.12 ERA, 1.48 WHIP and the league hitting .285 off of him in 81 career road starts
Nobody knows why the disparity exists, as Minute Maid Park is not really a pitcher's park, but the disparity is real over a fairly nice sampling.