Having regained sole possession of the AL West lead, the Los Angeles Angels will try to add a cushion before a pivotal series later this week.
Los Angeles (77-52) had its two-game lead in the division over Oakland erased with back-to-back road losses to the Athletics but avoided a sweep with a 9-4 victory Sunday.
Josh Hamilton homered and drove in three runs in the first four innings while staking the Angels to an early 8-0 lead. Mike Trout added his 29th homer - one shy of matching a career high - in his club's 10th win in 14 games.
Los Angeles will host Oakland for four games starting Thursday, but it will first play three against the Marlins (64-65), who are four games behind San Francisco for the second NL wild-card spot.
LeBlanc (0-0, 7.36 ERA) is making his first major league start since May 6, 2013.
He pitched 6 1-3 innings in relief of an ineffective Richards on May 30 and made his only other appearance this season for the New York Yankees on June 4 before being designated for assignment again. He was signed to a minor league contract by Los Angeles on June 17.
The Angels called up the 30-year-old LeBlanc on Thursday, a day after Richards suffered a season-ending knee injury. The left-hander has a big spot to fill - Richards was fourth in the AL with a 2.61 ERA and tied for the team lead with 13 victories.
"As important as Garrett has been, he's only on the mound once or twice a week. You understand that he's a big piece of your team, but there's guys who can step in and help us," third baseman David Freese told MLB's official website.
LeBlanc is 1-1 with a 5.60 ERA in three career starts against the Marlins, the most recent a 4-3 win for San Diego in 2011. He went 3-10 with a 4.30 ERA in 38 appearances, including 16 starts, for Miami from the beginning of the 2012 season until he was acquired off waivers by Houston in June 2013.
His former club is batting .300 and has produced 39 runs in its last six games but has lost three of its last four. The Marlins lost 7-4 to Colorado on Sunday despite having seven of their 11 hits go for extra bases.
Miami has dropped five of eight on the road but is 12-5 in interleague play, matching its most wins against the AL in one season. The Marlins, whose starters have compiled a 6.04 ERA in the last four games, send out Jarred Cosart (1-1, 2.45) - easily their most effective member of their rotation of late.
The right-hander has permitted one run in 13 innings in his last two starts. He gave up one run in six innings Tuesday against Texas, but the Marlins' bullpen couldn't protect a two-run lead in an eventual 4-3, 10-inning victory.
"I think we all knew that this guy's got great stuff," manager Mike Redmond told MLB's official website. "I think it's been fun watching him over the last couple of starts pitching when games mean something."
Cosart, acquired from Houston on July 31, went 0-2 with a 5.68 ERA in two starts against the Angels this season while with the Astros.