"He just really was pitching behind in the count, as were most of our pitchers that had trouble out there," Angels manager Mike Scioscia said.
Dodgers starter Aaron Harang allowed one run on three hits to get the victory. Harang struck out two and walked none in the first of two Arizona meetings between the two teams, and seventh-ranked prospect Chris Withrow added 2 2/3 innings of shutout ball.
"Harang was sharper today than his first start," Dodgers manager Don Mattingly said. "And Withrow looked good. He was really sharp. Chris may have the best stuff in the system. He has a chance to be really, really good. He's coming and what we're seeing is pretty good."
Weaver battled through a long first inning that saw him face eight batters. After stealing second base, Gordon scored on an Andre Ethier's double down the left-field line, followed by Rivera's double down the right-field line, scoring Matt Kemp and Ethier.
Weaver's day ended after a fielding error by third baseman Mark Trumbo, which would have been the final out of the second inning.
Angels catcher Chris Iannetta recorded the only extra-base hit off Harang to lead off the third inning and wound up scoring on a pair of groundouts, Erick Aybar's grounder to second bringing him home.
The Dodgers added a run in the fifth when Rivera grounded out to the right side to bring home Kemp for his second run of the game.
Sellers hit his three-run homer, his first long ball of the spring, in the sixth off Matt Shoemaker.
Up next for Dodgers: Chris Capuano starts for the Dodgers at home against the Colorado Rockies on Tuesday at 1:05 p.m. PT. He will be followed by relievers Ronald Belisario, Alberto Castillo, Stephen Fife and Matt Chico in a game that can be seen on MLB.TV.
Up next for Angels: Right-hander Dan Haren will face his former team when the Angels meet the D-backs at Salt River Fields on Tuesday at 1:10 p.m. PT on MLB.TV. Haren, who is expected to work three innings in his second Cactus League start of the spring, will be meeting right-hander Trevor Cahill, well known to the Angels from his previous years with the A's in the American League West. Among the other pitchers slated to get work for the Angels is veteran LaTroy Hawkins, looking to shake off a rough one-inning effort in his debut.