Clayton Kershaw returned to the mound for the first time in more than four weeks and left after five innings with more questions than answers, as he will be going for an MRI on his back Friday in Los Angeles. Depending upon the results of that test, the Dodgers' 2-1 loss to the Phillies on Thursday could be the least important aspect of the game.

Kershaw's line looked decent, considering the layoff: one run on four hits and one walk with five strikeouts, throwing 62 pitches, 42 for strikes, over five innings. Unfortunately for Kershaw, the final pitching line doesn't tell the entire story.

"Beyond frustrating," he said. "I felt like I was out of the woods. I was feeling good and then to have that crop up."

Kershaw’s back tightened up during his outing. They’re potentially going to do a scan. Taken out because of back, having not pitched in a month & his stuff “backing up” towards end of outing.
— Alanna Rizzo (@alannarizzo) 1 de junio de 2018

The Dodgers are likely to be overly cautious and not take any chances with their star pitcher. Kershaw has spent time on the disabled list the past two seasons with back injuries, including a prolonged stretch in 2016 due to a herniated disk. He also strained the teres major muscle in his upper back in the 2014 season opener in Sydney, Australia.

"Obviously with Clayton's history you want to make sure -- there is some concern," manager Dave Roberts said. "You want to make sure that he's well, so we're going to kind of dig into it and see if there is anything to it."

Clayton Kershaw velocity maxed out at 90mph left with back tightness will get MRI and not make trip to Denver........which clouds his 5IP 1 ER performance #Dodgers
— Jim Bowden (@JimBowdenGM) 1 de junio de 2018

Kershaw tried to take some of that history out of the equation.

"[The injury in] 2016 is entirely different. That was very, very severe," he said. "If I can compare it to anything, maybe comparing it to last year, maybe feeling it but it might not be that bad.

"My back has felt unbelievable until today. The shoulder is fine. ... I'm frustrated and disappointed that I can't contribute to the team. Being on the DL is no fun. ... But maybe I can avoid that, we'll have to see what happens."

I assumed the heaviest weight Clayton Kershaw carries is that he hasn't won the World Series. I was wrong https://t.co/vZMHo3aRPp
— Stephanie Apstein (@stephapstein) 31 de mayo de 2018

Thursday was Kershaw's first start since May 1, as he had been sidelined due to left biceps tendinitis. He is 1-4 with a 2.76 ERA in eight outings this season.

The three-time Cy Young Award winner wasn't throwing his fastball much Thursday, and when he did, it was topping out at 87-88 mph.

"I just saw that his stuff started to back up." Roberts said. "The fastball, slider and the curve, everything seemed to kick down a bit."

Clayton Kershaw, Super Nice 69mph Curveball. �� pic.twitter.com/ILmTERFAsu
— Rob Friedman (@PitchingNinja) 1 de junio de 2018

The injury bug has bitten the Dodgers throughout the 2018 season, as they are also missing starting pitchers Kenta Maeda (right hip strain), Rich Hill (blister on fingertip) and Hyun-Jin Ryu (groin strain).