Alvarez allowed one run on one hit with two walks while needing 27 pitches to get two outs against the D-backs. His second outing, Friday against the Rockies, went much smoother.
Alvarez, considered one of the organization's top relief prospects, needed 16 pitches -- 10 of which were strikes -- to get three outs in the Padres' 3-0 loss to the Rockies.
"I talked to [pitching coach Darren Balsley] and he told me to stay easy with my slider and not throw it as hard," Alvarez said of his plus-pitch. "And I was a little bit calmer out there."
Alvarez, a key piece the Padres obtained in the July trade with the Angels in the Huston Street deal, is a player the team wants to look at over these final three weeks. He could be a part of the bullpen picture next season.
"He had a good slider, even here in the Rocky Mountains, which I'm told is tough to do," said San Diego manager Bud Black, noting that it's hard for some pitchers to throw their breaking pitches at this higher elevation. "But we saw the ball down with the slider, the good velocity on the fastball.
"And the other night he might have been trying a little too hard."
Black has previously said the Padres could potentially look at Alvarez in some high-leverage situations late in games this month.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.