Pedro Guerrero hit a two-run homer, his second in as many games, and Jose Morales pinch hit a tie-breaking double for Los Angeles in Pittsburgh.
Morales' double with one out in the seventh scored Bill Russell, who had led off with a walk and advanced on Steve Yeager's sacrifice to make a winner of Bob Welch (1-2). The run came off loser John Candelaria (2-1).
Pirates Manager Chuck Tanner held a brief clubhouse meeting after the game, but said he wasn't angry at his team. The Pirates started the season 5-0 but have since lost seven of eight games, including five of six at home.
"I told them not to let a couple of games get them down," Tanner said. "We've only got 149 or 150 more games to go, and we're going to be a pennant contender capable of winning it all."
Tanner defended his decision to let Dave Parker, playing for the first time in two weeks, bat with two out and two on in the eighth against reliever Steve Howe. Parker, who had struck out three times previously, did so again on four pitches.
"He's a big guy on our club," Tanner said. "I've seen Parker get hits off Howe, off Steve Carlton, off a lot of left-handers. I told him not to worry about it, because he could come out here tomorrow and get four hits."