Rajon Rondo has probably been the biggest reason for the surprise success of the Chicago Bulls in their two-game series lead against the Boston Celtics, the top seeds in the Eastern Conference.Now, the Bulls will be without the veteran point guard.Bad news broke at Friday's shootaround in advance of Friday night's game at the United Center, just as the uneven season for Chicago seemed to be moving in the right direction in the postseason.Rondo suffered a fractured right thumb during Game 2 on Tuesday night and is out indefinitely, breaking the momentum for the Bulls.

Rajon had been averaging 11.5 points and 10 assists in the Bulls victories over the Celtics in Boston, and was a huge factor for the team's defense and rebounding.

Bulls coach Fred Hoiberg said Rondo has a cast and will be re-evaluated in 7-10 days. The problem is, the series could be decided before then.

Jerian Grant will start in place of Rondo in Friday's game, Hoiberg said.

Rondo had been a huge contributor in stopping Boston point guard Isaiah Thomas, who has been held in check compared to his lofty standards.

Through two games, Thomas has averaged 25.6 points per game through the first two, but went 7 of 13 on free throws in Game 2.

Rondo apparently suffered the injury during the third quarter of Tuesday's victory and played the rest of the way through the pain.

Who knows how long Rondo will be out, but the smart money is on the rest of the season, unless Chicago can make this run last quite a bit longer without him.

According to Chris Haynes of ESPN, the injury is a "pretty serious" one.

The Bulls will need Grant, along with Michael Carter-Williams and Cam Payne, to play well in Rondo's absence. Those aren't great bets.

Rondo was trying to get the Bulls past his former team, which he spent nine seasons with to start his career out of Kentucky.

After a few years of wandering around the NBA with the Dallas Mavericks, Sacramento Kings and now Chicago, Rondo finally seemed to be getting into his groove with the Bulls. He had played well late in the season and looked like his former self through two games in Boston.

Now, another unexpected twist to his career has Chicago fans worried about the present and could have them thinking what might have been in a winnable Eastern Conference.

It's a tough break, indeed.