There's little debate that Shaun Marcum has been the Brewers' most impressive starter thus far, and his first run through the National League has been incredibly fun to watch. Personally, I get disappointed when I have to miss a Marcum start.
Here's a question, though -- is his current success sustainable?
After throwing 8 innings of 1-run ball -- and 1 run that came on a wall-scraping home run -- Marcum's stats through 10 starts look incredible. He's striking out over 8.5 batters per 9 innings of work. He's walking just a touch over 2 batters per 9. His ERA is a sparkling 2.37, and his FIP is an impressive 2.70.
It was reasonable to assume that a move to the National League would help his numbers, but through 10 starts the results have been even more pronounced than expected. The K/9 is a batter higher than it was in 2010 (7.60 to 8.63). He's stranding 79.7% of the baserunners he allows, as opposed to 74.3% last year. The HR/FB rate has dropped from 9.6% to 6.0% this year -- that's what made Carlos Gonzalez's solo shot in the first so surprising. Always a flyball pitcher, Marcum has seen an increase in his flyball percentage -- from 43.3% to 47.4% -- but it appears most of that increase is due to a dramatic increase in his infield flyball percentage (in other words, they're flyballs, but they're not being hit hard).
The fact that Marcum is getting such good results through his first 10 starts is obviously good for the Brewers, but it isn't crazy to be worried about a little regression, too. He's a pitcher that most NL batters are seeing for the first time, and it will be interesting to see how teams fare against him when they see him for a second or even a third time. He's already faced Houston and Atlanta twice and actually fared better the second time around, but it will be interesting to see how he does against teams like the Reds, who were able to wear him down in his first start by being incredibly patient at the plate.
So far, opponents have only been able to hit .263 on balls in play against Marcum, which is low compared to league averages. We may not have to worry about that number crashing back to Earth, though, because in over 650 career innings, opponents have only been able to hit .270 on balls in play against Marcum.
What I do worry about, though, is the home run rates returning to normal. The 6.0% HR/FB is so far below his career average of 11.0% that you figure it almost has to regress at some time. The same could be said for his home runs allowed per 9 innings, which is currently sitting at 0.70, but his career average is 1.25 and he's never posted a rate lower than 1.1.
However, the good news with Marcum is that he will likely continue to keep runners off the bases, so if he does start giving up more home runs, they probably won't be three-run shots. His xFIP -- which normalizes the HR/FB rate to 10.5% -- is still a very good 3.16. Even if his HR numbers regress to career norms, he has still set himself up to be one of the best pitchers in the National League this season. Considering Yovani Gallardo has struggled to start the year and Zack Greinke is still trying to build up stamina, Marcum's strong start has been the key to keeping the Brewers in the NL Central race.