"Really gutsy performance," Arizona catcher Chris Iannetta said. "I know he wasn't 100 percent and I just think he went out there and battled and he gave us everything he had, which we're really thankful for."
Walker said he initially tweaked his back while swinging at a pitch in his last start against the Giants at AT&T Park.
"Just swinging too hard and trying to do too much," said Walker, who before this year had spent his career in the American League. "I got to know my limits and know my place as a hitter. My job is to go out there and pitch. I want to make sure I can go out there every fifth day and pitch. It's good to get offense, but my job is to go out and pitch."
There was no issue with his pitching Sunday.
Walker got himself into trouble in a couple of innings. He loaded the bases with two outs in the first, but struck out Joc Pederson to end the threat.
"They have a really tough lineup," Walker said. "They fouled off a lot of real good pitches. A couple of their hits, I thought, I jammed them. I made good pitches and I jammed them, but they found holes. I stayed within myself, made pitches and really went after it."
After retiring the Dodgers in order with relative ease in the bottom of the fifth, Walker was removed for a pinch-hitter with the bases loaded in the top of the sixth and Nick Ahmed grounded into an inning-ending double play.
"I thought his last inning was his best inning," D-backs manager Torey Lovullo said. "Unfortunately, he got a little low back tightness. Nothing alarming, but it was one of those things that we didn't want to escalate, but because of the situation, as well, we thought it was the right move to take him out of the game."
Walker's next scheduled start is Friday, when the D-backs open a three-game series with the Dodgers at Chase Field and the back should not be an issue.
"I'll be ready for my next start," he said.
Steve Gilbert has covered the D-backs for MLB.com since 2001. Follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.