Losing A.J. Burnett for a month could cost Pirates their wild-card lead

The news that the Pittsburgh Pirates will miss veteran righty A.J. Burnett for at least four weeks with a flexor strain in his right elbow represents good news and bad, depending on whether or not you're the half-empty or the half-full type: It's good news that he's not done for the year (and possibly his career, given how often he talks about retiring), but it's bad news because of what a critical part he's played as one of the top starters on the second-best team in the National League.

With Burnett taking his turn every fifth day, the Pirates' rotation ranks fourth in the majors in starter ERA (3.33), trailing just the Cardinals, Dodgers and Athletics. The rotation was also tied for third in quality starts with 64 in their first 104 games. While Burnett's overall performance numbers have slumped after a tough month (posting a 6.60 ERA in his last five starts), Burnett was the critical third man behind staff aces Gerrit Cole and Francisco Liriano. That's a role that's even more important in short-season October baseball when fourth starters might make a start per series and fifth starters get dropped altogether. If the Pirates had lost Burnett for more than the next four to six weeks, then Charlie Morton would move up a peg in the postseason picture, while Jeff Locke or deadline addition J.A. Happ might have to start in October.

But first the Pirates have to get there, and while they're one of the NL's best teams at the moment and should be able to bank on a wild-card bid, the timing for Burnett's injury probably couldn't come at a worse time. That's because they're heading into an especially tough three-week stretch on the schedule, facing the Chicago Cubs, Los Angeles Dodgers, St. Louis Cardinals, New York Mets, Arizona Diamondbacks and San Francisco Giants over their next 19 games. That's two first-place teams, three wild-card contenders who would like to take the Pirates down a peg and a tough Snakes club. Even with a four-game lead in the wild-card hunt over the Giants and Cubs, that stretch already represented a big challenge for the Bucs with Burnett. Seeing Happ start every fifth day, it just got a little bit bigger.

Burnett's woes are just the latest addition to a stack of injuries piling up on the Pirates. With injuries to both third baseman Josh Harrison (thumb surgery) and shortstop Jordy Mercer (sprained knee), the left side of their infield won't be back in action until early September, if then -- and after the point in time when they might be able to get in some live-game action on rehab assignments in the minors, meaning that both will return to the Pirates' stretch run without reps to get up to speed.

Why bring their absences up? Because the Pirates' infield is a key element in the success of the most-ground-ball dependent team in the league. That's important as well for a Pirates team that, despite its aggressive use of performance analytics to help its defense, ranks just 24th in Defensive Efficiency overall, and is now relying on Jung Ho Kang (seen as stretched at short) and newly added Aramis Ramirez (a long-standing defensive liability) to replace Mercer and Harrison.

Maybe that won't matter; Happ's a fly-ball guy, after all. Except that he's coming to the Pirates and leaving behind the comfort of pitcher-friendly Safeco Field in Seattle. So set your expectations for Happ to "modest" for the journeyman lefty. Can Happ -- or even swingman Joe Blanton -- fill the gap? We're talking about at least a half-dozen turns, but I wouldn't be too optimistic they'll be more than what they are, which is interchangeable No. 5 types in a second-division rotation and guys an offense needs to work to outscore to win their starts.

The next three weeks will tell how big an impact this will have. But if you're looking for a reason why the Pirates may come back to the pack in the NL wild-card race, this is it. Here's a prediction: Unless the Pirates' offense goes nuts this month, that race just got a whole lot closer.

Christina Kahrl writes about MLB for ESPN. You can follow her on Twitter.