Though Doolittle's velocity wasn't all the way back, the lefty consistently hit 92-93 mph on Sunday. After falling behind, 3-1, to his first batter, Yasmany Tomas, Doolittle fired back with a pair of fastballs for strikes, with Tomas swinging through the last one.
Doolittle then got Nick Ahmed to fly out on just two pitches and needed only three to set down A.J. Pollock on strikes.
"He got to a three-ball count, got the out," Melvin said. "I know he feels a lot more comfortable coming into a game like that, which he really hasn't to this point. He needed to be perfect, and he was. It's a big step for him."
Melvin still foresees Doolittle closing games again before season's end. In the meantime, another lefty has impressed.
Before giving up the tying run in the ninth inning Sunday, Drew Pomeranz had posted a 0.73 ERA in his previous 11 appearances. On Saturday, he struck out the side on just 11 pitches in the ninth inning of a 3-2 victory, securing his third save.
"Last night he pitched like Doolittle," Melvin said. "All fastballs, was able to elevate, had life on it. He's holding down the fort here recently very well."
The A's have tried out several different arms in the closer's role this season in place of Doolittle, who has pitched just three times because of two lengthy disabled list stints, but none have showcased overpowering stuff like Pomeranz, who is making his case as a future full-time closer.
Pomeranz hit 95 mph Saturday, throwing 10 of his 11 pitches for strikes. Melvin also said, "It seems like every time he's out there he's more and more comfortable."
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.