With nobody out in the sixth, Gordon uncorked a pitch over the head of catcher Miguel Montero, who retrieved a fortuitous bounce and shoveled to Gordon to retire Rickie Weeks, charging from third. Gordon collapsed after applying the swipe tag, holding his hamstring area.
Gordon signed a one-year deal in the offseason.
"I was coming home, and once I got ready to slow down, I kind of felt something," Gordon said. "You work so hard on your elbow and work so hard coming back from surgery, and for something else to happen, it kind of gets you down a little bit. I'm definitely down about it, but my spirits are still high. Kenny [Crenshaw, trainer] is someone that I've gotten to know the last couple months and gotten to know really well with my elbow, so I know he can help me figure this out."
The play itself loomed large in the seventh, when Arizona hit a trio of solo home runs to tie the game at 3-3. Jon Rauch entered to conclude the sixth without allowing any damage.
"He didn't look like he had his best command, but something like that where he covers the plate and gets an out, maybe that gives you a little resurgence, but obviously he's going to be out for a while," Melvin said.
Gordon made his last appearance Thursday, allowing four runs in the seventh that helped Milwaukee claim a 4-1 win.
Gordon said his stuff "was probably the best I've had in a long time" Sunday, and the errant toss (it wasn't ruled a wild pitch, because the out was recorded at home) was the result of trying to come up and in for the first time since his return.
"I was trying to throw a pitch I hadn't thrown in eight or nine months," he said. "It's a pitch that's always worked for me, and it's just taking me a little bit of time to get the command with the pitches that I want to have.
"The thing is, my arm feels really good. The good thing is that I'm ahead of schedule for the most part. I don't know if I feel that, but I believe it."
Gordon admitted the ailment hurt much worse after the game than after the initial strain. He said the injury would be re-evaluated Monday to determine a definite course of action.
The Brewers won the game, 4-3.