Crisp was injured Friday while making a headfirst dive while trying to steal second base against San Francisco. He was hit on the hand by Giants second baseman Juan Uribe's glove and was called out.
The initial diagnosis was a dislocated finger, but X-rays revealed the fracture.
"It's very disappointing," said Crisp, who is expected to be out one to two months. "I'll always say I'll be a good player if I can just stay healthy. I just can't get that good break. I always get the bad one."
The A's made several other moves, including designating veteran DH Jack Cust for assignment. Cust, who signed a $2.5 million, one-year contract with Oakland on Jan. 7, went 0 for 4 with three strikeouts in the A's 10-6 loss to San Francisco on Saturday and nearly collided with center fielder Rajai Davis in the ninth inning.
"I wasn't swinging the bat well," said Cust, who was informed of the decision after meeting with A's manager Bob Geren and general manager Billy Beane. "I was pretty surprised, but I've played this game long enough to know that anything can happen."
In addition to Crisp, Oakland placed four players on the DL including pitcher Trevor Cahill. The right-hander, who was a candidate for the fifth starter's spot before giving up five earned runs in two innings against the Giants on Saturday, has a left scapula stress reaction. Right-hander Joey Devine, left-hander Josh Outman and right-hander Michael Wuertz were also placed on the DL.
The most surprising move was the decision to part ways with Cust, who was designated for assignment to make way for Eric Chavez, Oakland's six-time Gold Glove third baseman who spent most of spring training alternating between first base and designated hitter.
"Basically I'm going to give Eric Chavez a chance to be the DH and take that road first," Geren said. "To get both of them the [at-bats] to earn that job is impossible in the season right now. We made that decision and we go from there."
If Cust clears waivers, he can accept a minor league assignment from the A's and could possibly be back with the big league club if Chavez struggles.
Crisp signed with Oakland in the offseason and was coming off surgery to both shoulders. He was slowed by a tender hamstring early this spring and didn't play the outfield until late March.
Expected to be the center of the A's new offensive philosophy focusing on speed, Crisp batted .432 with two homers and eight RBIs in the spring.