Rodrigo Lopez, on paper, looks like a reasonably average pitcher. Lifetime ERA of 4.36, WHIP of 1.36, BAA .267, 6.2 K/9IP, 2.9 BB/9IP, for a 40-33 record (not bad considering his team). His numbers are a bit better if you remove his 6 games pitched for the Padres in 2000 and only look at his career with the Orioles (2002 and since): ERA of 4.18, etc.
Against the Red Sox, at first he only looks marginally different. His ERA is quite a bit better -- 3.73, but most of the other numbers are about the same: 1.36 WHIP, .259 BAA, 6.1K/9IP, 3.2 BB/9IP. Record vs. the Sox of 9-4 (though it feels like 12-1 or so). But a couple things stand out...
- On April 26 of this year he got shelled by Boston, 8ER in 3.1 IP. Take out that one start (out of 15), and his ERA against the Sox is 3.12.
- In his MLB career, he's started 94 games, and pitched 610.1 innings. Against the Red Sox, he's started 15 games, and pitched 101.1 innings. So as a major leaguer, nearly one-sixth of his pitching has been against the Red Sox.
- Over the course of his career, he's given up 1.17 HR/9IP. Against the Sox, that number is more than halved: 0.53HR/9IP. Since 2002, the Sox have hit 1.3HR/9innings.
- Looking just at his pitching in Fenway: in 9 starts (58.2 IP, or 10% of his career IP) his WHIP is 1.24, BAA is .230, and ERA is 2.91. He's 6-1 there, meaning at Camden Yards he's 3-3 with a 4.81 ERA against the Sox. He's only given up two home runs at Fenway, or 0.31HR/9IP.
Okay, so maybe 58.2 IP is too small a sample size. But so far he seems to be utterly dominant in Fenway, against Red Sox teams that were built for hitting there.
His contract with the Orioles ends after the 2005 season.