Richards was called up from Triple-A Salt Lake on Tuesday to replace Weaver, who injured his back on his 12th pitch during Monday night's 9-8 Angels win.
In 10 starts this season in Triple-A, the Angels' No. 2-ranked prospect is 5-2 with a 4.31 ERA, striking out 48 while walking 29. Richards impressed in Spring Training, but after getting off to a solid start in Triple-A, he has run into some trouble of late, posting a 7.06 ERA over his last six starts.
"It's a good experience pitching in Triple-A," Richards said. "With the [Pacific Coast League] being a hitters' league, it kind of forces you to tighten up your pitching a little bit, work on specific stuff as far as getting ahead of hitters and throwing the ball down in the zone."
During his callup last season, the Riverside, Calif., native pitched in seven games, starting three, and went 0-2 with a 5.79 ERA.
Manager Mike Scioscia said the righty will be available out of the bullpen for a couple of days until he has time to figure out when he'll need a fifth starter. Tuesday starter Dan Haren could pitch Sunday's series finale against the Rangers, but the Angels will need a No. 5 guy by Tuesday.
While in Salt Lake, Richards has worked on slowing the game down and not allowing the pace of it to dictate how he pitches. While at times last season he stuck to a three-pitch repertoire in the Majors -- fastball, changeup, slider -- he has worked on his curveball a lot more, throwing it for strikes and as an out pitch.
Though getting the callup for an injury isn't the ideal situation for him, Richards said he can't think about it. With the team riding a seven-game winning streak, he has got to be ready to pitch in any situation.
"It was a learning experience last year," Richards said. "This year, I feel like I'm a lot more prepared coming into it."