Ouch. (Michael Dwyer/AP)

Up 2-0 in their Eastern Conference first-round series with the top-seeded Boston Celtics, everything seemed to be going well for the No. 8 Chicago Bulls. And then Friday morning happened.

In a statement, the Bulls said their starting point guard underwent X-rays after Tuesday’s 111-97 victory over the Celtics in Game 2 but won’t require surgery. However, a source told ESPN’s Chris Haynes that the fracture — suffered in the third quarter, Coach Fred Hoiberg said — is “pretty serious” and his return will depend on how far the Bulls advance. Hoiberg added that Rondo is in a cast and will be reevaluated in seven to 10 days.

“It shows the toughness of Rajon Rondo to continue to fight through and battle and play pretty much the rest of that game,” Hoiberg said.

Rondo finished Game 2 one rebound shy of a triple-double and is averaging 11.5 points, 10 assists and 8.5 rebounds in Chicago’s two playoff wins.

He’s also been stout, defensively.

Jimmy Butler is expected to be the team’s primary ballhandler in Rondo’s absence and Jerian Grant will slide into the team’s starting lineup after playing just six minutes in Game 2. He’ll be tasked with guarding Celtics point guard and leading scorer Isaiah Thomas.

Chicago has had point guard difficulties all season, going through six of them — Rondo, Grant, Michael Carter-Williams, Spencer Dinwiddie, Isaiah Canaan and Cameron Payne (who will be active for Game 3) — after failing to find a suitable replacement for Derrick Rose last summer and then signing Rondo and Dwyane Wade to cap-eating deals.