Pedro Baez pectoral injury could have Kenley Jansen back Friday

They had performed better than anyone really dared imagine, including the Dodgers.

“We came out of spring training not really knowing what we had,” said Manager Don Mattingly of the bullpen, which had been the great black hole of the Dodgers’ 2014 season.

Thus far -- playing without injured closer Kenley Jansen -- it has been just short of brilliant. The Dodgers went into Wednesday with a bullpen earned-run average of 1.94, third-best in baseball.

One of the key relievers had been Pedro Baez, the converted third baseman who was lighting up radar guns. In 15 games this season (15 1/3 innings), Baez has struck out 22 and walked three, fashioning a 1.76 ERA.

Only Wednesday night he left the game against the Miami Marlins in the eighth inning because of what the Dodgers described as a right pectoral injury. Baez summoned catcher Yasmani Grandal to the mound. Grandal promptly called for trainer Stan Conte, who quickly exited with Baez to the clubhouse.

“He felt something up in his peck there,” Mattingly said. “He’ll get that looked at tomorrow, but the fact he left the game like that, it’s not that great.”

Mattingly said Baez would likely have an MRI exam on the chest muscle Thursday.

If Baez is headed to the disabled list, that could hasten the return of Jansen by a day. Jansen, recovering from foot surgery, completed what was scheduled to be his final rehab appearance Wednesday for Class-A Rancho Cucamonga. He threw one perfect inning, striking out two.

Jansen was originally expected to return to the roster Saturday. Mattingly said Jansen would not be activated Thursday, but could be on Friday.