An already frustrating season for Madison Bumgarner took another turn Sunday afternoon when back spasms hampered the veteran left-hander and forced him to leave the D-backs’ 9-5 loss to the Padres at Petco Park.

Bumgarner woke up in the middle of the night and felt some discomfort in his mid-back area but thought he had slept funny and went back to sleep.

It was still somewhat sore in the morning, but after receiving treatment from the team’s medical staff, he thought he would be OK to pitch.

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“Good enough where I thought I would try to go out there and give us what I could and, hopefully, try to save the bullpen a little bit and try to keep us in the game,” Bumgarner said. “[And] I wound up doing neither one. It would grab me at what seemed like random times to me. One delivery it seemed like it might kind of grab me is how I would describe it. Then the next one it wouldn’t do it at all, but you’re waiting for it. It was tough. It was aggravating.”

According to manager Torey Lovullo, Bumgarner will head back to Phoenix to have his back further evaluated.

Bumgarner struggled in the first inning, allowing a solo homer to Manny Machado and a two-run homer to Wil Myers. Between innings, television cameras caught Bumgarner talking with athletic trainer Ryan DiPanfilo and Lovullo.

Eventually, Lovullo elected to send Bumgarner back out for the second inning, and the left-hander allowed another two homers and three additional runs. Lovullo then made the decision to pull him before the third with the D-backs down 6-0.

“I kind of liked what I heard from him,” Lovullo said of the first-inning conversation. “I thought it was good enough to go back out there, and, obviously, that wasn’t the case. I’m going to wear that one a little bit.

“I’m still getting to know Bum. I love his makeup and his aggressive mentality. I’ll have to think twice about it if it comes up again. I wish I had made a different decision. It’s the one I made, and I’ve got to live with it.”

Lovullo wasn’t the only one who wanted a do-over on it.

“Obviously, hindsight is 20-20,” Bumgarner said. “We’re sitting here, and it looks like, obviously, I should not have been out there. At the time, me, I feel like I can find a way and get guys out and keep us in the game, and it just didn’t work out that way.”

Back issues are not something that Bumgarner has had in the past, and this is yet another challenge for him in what has been a difficult first year in Arizona after he signed a five-year, $85 million free-agent deal in the winter.

Before Sunday, the biggest concern was Bumgarner’s velocity, which was the lowest of his career.

He was hitting 91-92 mph on the radar gun during Spring Training, but that dipped after he returned to action following the COVID-19 shutdown. In his first two starts of the year, he averaged a career-low 87.9 mph with his four-seam fastball despite feeling healthy.

It dipped even lower to 87.1 mph Sunday, but he said this time that was the result of the back issue.

Add it all together and Bumgarner’s 2020 has been filled with frustration.

“Coming to a new place, wanting to do good, and then this type of season on top of that,” Bumgarner said. “It’s just, none of it has really went the way I wanted it to go. You’ve got to just roll with it and try to do the best you can. That’s what I’m doing -- trying to get to where I want to be and need to be to give these guys a chance to win when I go out there.”

Whether Bumgarner makes his next start in five days will depend on what the doctors say, but Lovullo said right now the concern level is “minimal” that it’s anything serious.