He's had an interesting career. He was drafted by the Mets in 1995 then traded to the Marlins in 1998 for Al Leiter during one of the their hey-we-won-the-World-Series-let's-blow-up-the-team purges following the 1997 season. (Mission accomplished: the team went from 92-70 in 1997 to 54-108 in 1998.) Burnett was a 22-year-old rookie when he got seven starts in 1999. After seven years with the Marlins, he became a free agent and signed a three-year contract with Toronto for $28.6 million after the 2005 season. He went 38-26 with a 3.94 ERA over 80 starts for the Blue Jays and became a free agent again, signing with the Yankees for five years at $16.5 million per year in December 2008. That didn't go so well. He was OK his first year in the Bronx, going 13-9 with a 4.04 ERA in 2009, below the league average of 4.45, and getting a win in the second game of the World Series that year. It spiraled downhill from there, with ERAs of 5.26 in 2010 and 5.15 in 2011. The Yankees gave up on him, sending him and most of the cash needed to pay his salary to Pittsburgh for two minor leaguers who've never appeared in the majors.
In Pittsburgh, he had a renaissance, going 16-10 with a 3.51 ERA in 2012 and 10-11 with a 3.30 ERA in 2013. Going into the 2014 season, when he'd be 37, a lot of folks figured he's re-sign with the Pirates, but the Pirates didn't offer what he wanted, there were stories of hurt feelings, and he signed a contract with Philadelphia that paid him $15 million last year. His contract gave him a $12.75 million option for 2015, but he declined it and instructed his agent to negotiate a deal with the Pirates, saying, "I've got one more [season] in me. There's no other place I'd rather be to finish my career," and "I want to be in a place where I'm really happy...this is where I belong." He signed for $8.5 million, effectively taking a $4.25 million pay cut to go back to Pittsburgh.
Here are the stats for Burnett's past five seasons: Two with the Yankees, two with the Pirates, one with the Phillies.
The key question for the Pirates and their fans is whether Burnett can return to his 2012-2013 form. Over at Gammons Daily, David Gobiewski wrote a great piece summarizing Burnett's prospects in general. I want to focus on what went right in Pittsburgh and what went wrong in Philadelphia.
I'll start with a table. GB% is the percentage of the balls in play off Burnett that were ground balls. GB/FB is the ratio of ground balls to fly balls. HR%, SO%, and BB% is the percentage of batters who hit home runs, struck out, or walked against him. HR/FB% is the percentage of the fly balls he allowed that went over the fence. The last four columns are pitch mix: FB% is fastballs, SI% is sinkers, CH% is changeups, and CU% is curveballs.
Provided by Baseball-Reference.com (HR%, SO%, BB%), FanGraphs (GB%, GB/FB, HR/FB%), Brooks Baseball (FB%, SI%, CH%, CU%)
Additionally, the Pirates have one of the more analytically-oriented front offices, and they shifted their infielders 500 times in 2013, usually moving them to the right of second base when a lefty swinger who tended to pull was at the plate. Shifting helps ground ball pitchers record outs. When Burnett joined the Phillies, he went to a team that shifted only 45 in times to 2013. They bumped that up to 291 in 2014, sixth in the league, but still well below the Pirates. So it's reasonable to think that he lost some ground ball outs when he moved across Pennsylvania.
Plus, the Pirates play in one of the toughest parks in the majors in which to hit home runs. PNC Park depressed home runs by 30% in 2014. The Phillies play in Citizens Bank Park, which boosted homers by 18%.
So that's what happened to Burnett: He generated fewer ground balls, which were hit into an infield that was less well-positioned to field them, in a home park that helped homers.
That doesn't really tell the whole story, though. He relied on his sinker more in Philadelphia than he ever had before, which should have kept his ground ball rate up. Instead, it fell. And while his home run rate rose from 2013 to 2014, it was lower than it was in 2012, when he was good.
I think there were two problems. First, his sinker failed to generate the same results: 13.2% of his sinkers resulted in ground balls in Pittsburgh, and just 9.7% in Philadelphia. As a result, it became easier to hit, as he allowed 29 doubles, three triples, and 11 homers off the pitch in 2014 after allowing 30 doubles, four triples, and 14 homers in 2012 and 2013 combined.
Second, he had problems with the strike zone. His percentage of pitches in the strike zone fell from 51% in 2012 to 49% in 2013 to 47% in 2014. More importantly, batters stopped chasing his pitches outside the strike zone, as his percentage of swings on pitches outside the strike zone fell from 29% in 2012 and 31% in 2013 to 27% in 2014. That resulted in a big boost in his walks (he led the league in walks allowed), and more baserunners resulted in more runs scoring.
So I wouldn't expect anything magical from Burnett's return to Pittsburgh. Yes, he'll benefit from being a tougher park in which to hit a home run. And playing with a shifted infield behind him (the Pirates led the league in shifts last year) will take away some of those base hits. But pitching coach Ray Searage's focus won't be on changing the pitches that Burnett throws as much as changing their effectiveness--specifically, throwing more of them in the strike zone and locating them in order to induce more ground balls. Doing that with a pitcher who turns 38 in January won't be easy. I expect an improvement but not a return to Burnett's 2012-13 heyday.