Jay Bruce’s lower back was sore when he arrived at Citi Field on Friday and only worsened as the day progressed.

By the fourth inning, he was ready to call it a night, knocked out by back spasms following his second at-bat against Cubs’ right-hander Tyler Chatwood.

“It just wouldn’t loosen up on me,” Bruce said following the Mets’ 7-4 loss. “I really don’t anticipate it being serious.”

Manager Mickey Callaway tentatively has Bruce scheduled to play Saturday, but the outfielder will be evaluated when he arrives.
Bruce had started at first base Thursday — it was only his second start of the season at the position — and indicated his back spasms may have resulted from not stretching properly.

“I am going to have to be more proactive with the stretching if I am going to play first base,” Bruce said.