Zack Greinke, the offseason acquisition the Milwaukee Brewers hoped would put them over the top in their pursuit of an NL Central title, is expected to begin the season on the 15-day disabled list after suffering a hairline fracture in one of his ribs playing pickup basketball.

The Brewers previously had said only that Greinke suffered an injury a couple of weeks ago during an off-the-field activity, but Greinke didn’t receive the diagnosis of a broken rib until Tuesday, just after the team’s Cactus League game with the Los Angeles Dodgers. At that point, Greinke told reporters he suffered the injury going for a rebound during a basketball game, before he pitched in any spring training games.

“Everyone always told me not to do it because I was going to get hurt,” Greinke said. “It finally caught up to me.”

Greinke, not knowing how severe the injury was, made two spring training starts after being hurt, allowing a total of one run on six hits over 3 1/3 innings. Now that the hairline fracture, which is between the seventh and eighth ribs on his left side, has been diagnosed, Greinke is expected to miss four to six weeks, which means he likely will begin the season on the 15-day disabled list.

“I’m feeling good but it’s not worth it,” Greinke said. “Hopefully it won’t be too long. I don’t want to miss any time with the team, especially at the beginning. Until it heals there’s nothing you really can do. You just need to let it heal.”

The Brewers acquired Greinke on Dec. 19, prying away the 2009 AL Cy Young award winner by sending four prospects to the Kansas City Royals.

The small-market Royals were actively looking to unload the 27-year-old righty due to his expected contract demands. In return, Kansas City received two promising major leaguers in center fielder Lorenzo Cain and infielder Alcides Escobar and two pitching prospects and former first-round draft picks in right-handers Jake Odorizzi and Jeremy Jeffress for Greinke and veteran shortstop Yuniesky Betancourt.

The move immediately put the Brewers among the favorites to win the NL Central and return to the playoffs for the first time since 2008.

“It doesn’t matter how he hurt it,” Brewers manager Doug Melvin said. “This is part of what we go through as a GM.”Greinke, drafted sixth by the Royals in the 2002 draft, went 10-14 with a 4.17 ERA in 2010, one year after his Cy Young campaign.

–Tony Jackson covers the Dodgers for ESPNLosAngeles.com. Follow him on Twitter. Information from The Associated Press was used in this report.