As the thick of inter-league play rolls on, there is a heavy urge to compare the two leagues because they are different. I assume that common assumption is that the American League is harder to pitch in because of the DH and notable offensive powerhouse clubs like New York and Boston. I also assume that this is the reason why few starters make the switch from the NL to the AL for the first time every off-season. Hardball Times own Fantasy writer Derek Carty looked into this awhile ago and found out that pitchers can be expected to improve their ERA .41 points moving from the AL to the NL. Their strikeout rates rose up slightly while their walk rates decreased slightly while making the same move. Also pitchers see their BABIP drop and Left On Base Percentage (LOB%) go up in the NL. So overall, a pitcher can be expected to improve their performance moving from the AL to the NL.
Prior to this season, there were a total of just four starting pitchers who switched leagues for the first time. Those pitchers were Roy Halladay, Max Scherzer, Ian Kennedy, and Ben Sheets. Sheets was the only one acquired via free agency as the other three moved in trades. So here is a look at the numbers for each pitcher this season compared to their previous seasons. First up, the two moving to the NL from the AL.
This is the big gun of the group. Unlike CC Sabathia and Cliff Lee, Halladay's switch came during the off-season allowing him to be moved to a contending team for a full season (although the Phillies currently sit at third place). Halladay, known for his ability to dominate and pitch deep into the game consistently, had displayed it well in his first eleven starts with five complete games and three shutouts which is one shy of his career high of four which he achieved last season. A little cool off in June hasn't hurt his numbers.
AL Career 148-76 W-L, 3.43 ERA, 3.45 FIP, 3.29 K/BB
NL 2010 8-5 W-L, 2.36 ERA, 2.62 FIP, 5.63 K/BB
It is a small sample size, but Halladay is pitching slightly better than last season and overall better than his career mark in 13 seasons with the Jays.
A valued prospect at one point, once sharing the spotlight with now Yankee starter Phil Hughes, Kennedy was moved in the big three team trade that led him from New York to Arizona. Kennedy didn't pitch much in New York due to injuries and lack of open rotation spots, but he is now pitching in the Majors for a full season for the first time and has now pitched in as many games as he had in three seasons with the Yankees.
AL Career 1-4 W-L, 6.03 ERA, 4.93 FIP, 1.16 K/BB
NL 2010 3-4 W-L, 3.57 ERA, 4.68 FIP, 2.48 K/BB
Kennedy's FIP hasn't improved that much due to a ballooned home run rate 1.5 per nine innings this season, but his ERA was cut almost in half while he lowered his walk rate and increased those Ks.
Now for the two pitchers who switched from the NL to the AL
Sheets had a nice run with the Brewers, riddled a bit with injuries later on then missing the entire year last season. For a hefty $10 million, the Oakland A's signed him with sub-par results.
NL Career 86-83 W-L, 3.72 ERA, 3.54 FIP, 3.85 K/BB
AL 2010 2-7 W-L, 4.95 ERA, 4.84 FIP, 1.65 K/BB
Not a good season for Sheets. The velocity on his fastball is down a mph from 2008 and his xFIP is now at a career high for a single-season.
Scherzer busted onto the scene in his first full season in the Majors last year with the D-Backs striking batters aplenty with a 9.19 K/9 after quick accession in the minors. As part of that three team trade that included Ian Kennedy and Edwin Jackson, now Detroit Tiger Max Scherzer had struggle tremendously in his first eight starts prompting a demotion to Triple-A. He was called up about two weeks later and has improved even striking out 14 batters in his return start on May 30.
NL Career 9-15 W-L, 3.86 ERA, 3.53 FIP, 2.86 K/BB
AL 2010 3-6 W-L, 6.14 ERA, 4.95 FIP, 2.36 K/BB
Scherzer's walk rate hasn't changed, just his strikeouts are 1.5 K/9 and he has given up almost half of last season's home run total. His struggles early may be due to a decrease in his fastball velocity, but he has picked it up to last year's level.
These four pitchers pretty much followed the assumed standard. But it is only a small sample I looked at here and I could have included a few more pitchers who switched leagues even though they pitched briefly in that league early in their career, like Carlos Silva. Or not.
Read more great baseball stuff at The Hardball Times.