Cabrera underwent an MRI exam on Tuesday in Cleveland, and the results confirmed the initial diagnosis.
"He got scanned and, as expected, he did some damage in there," Indians manager Terry Francona said.
Francona would not speculate about how much time Cabrera might miss, but the manager did note that Cleveland's medical team indicated that similar quad injuries have required three to four weeks of recovery time. The manager emphasized that there is currently no timetable for Cabrera's return.
"It's just going to be on how quickly he heals," Francona said. "Nobody knows that, so that's just kind of where it is. ... It could be three to four weeks, but again, that's a guess on their part, and in all fairness to Cabby, it heals when it heals. We'll hope for the best."
In the fifth inning of Monday's 7-4 loss in New York, Cabrera's quad injury flared while he was sprinting to first base on a groundout. The shortstop pulled up before reaching the bag and nearly tripped as pain shot through his leg. Cabrera needed to be helped off the field, and he indicated after the game that his leg was still very sore.
Cabrera has been dealing with the quad injury off and on since late April.
Francona indicated that infielder Mike Aviles will assume the regular role at shortstop while Cabrera is out. Aviles, who served as the everyday shortstop for the Red Sox last season, entered Tuesday's action hitting .283 with three home runs, six doubles, 16 runs and 18 RBIs in 39 games this season for the Tribe.
"That's the good side of this," Francona said. "Not only is [Aviles] talented enough to do it, but he has worked hard enough so you put him in the lineup and his body won't [break down]. Some guys can do it, but they're not ready to play every day. He works so hard that he won't miss a beat."
With Cabrera out, Francona put left fielder Michael Brantley in the third spot of the lineup for Tuesday's game.
Through 53 games with the Tribe this season, the switch-hitting Cabrera was batting .254 with five home runs, 18 doubles, 25 RBIs and 28 runs scored. He leads the Indians in doubles and extra-base hits (25) and boasts a 33-game errorless streak at short. Dating to May 9, Cabrera has hit .295 (28-for-95) with 13 extra-base hits in 24 games.
Cabrera was named to the American League All-Star team in each of the past two seasons.
Diaz, who was called up in May last season while Cabrera battled through a hamstring issue, was hitting .211 (40-for-190) with four homers, eight doubles and 18 RBIs in 52 games for Columbus this season before being recalled. In five games with the Tribe last year, he posted a .267 (4-for-15) average. Diaz will serve as the primary backup shortstop for the time being.
"He wasn't swinging it terribly well in Triple-A; that happens," Francona said. "Mike Aviles is going to get the majority of the playing time, but that depends on things happening, too. The nice thing is that this is where the versatility of our club should help us a lot."