What was arguably the Braves’ biggest strength just got a little stronger.

The team made a move to improve the majors’ top-rated bullpen on Monday by trading for left-hander Scott Downs from the Los Angeles Angels in exchange for minor league reliever Cory Rasmus.

Downs, 37, has a 1.84 ERA in 43 appearances, with a .243 opponents’ average including .196 against left-handed hitters.

“I played with him the last two years and he’s pitched lights-out over there,” said Braves setup man Jordan Walden, a former Angels teammate of Downs. “Very good sinker and good curve. Pounds the sinker in on lefties.”

Downs is owed a little less than $2 million of his $5 million salary and will be a free agent after the season. The Braves wanted to acquire a proven left-hander to take some of the load off standout rookie Luis Avilan, their only lefty reliever since Jonny Venters and Eric O’Flaherty had elbow surgeries early in the season.

“We put a lot of stressful innings on a young kid (Avilan), so to bring in a veteran guy who can take some of the burden off him is a really good move,” manager Fredi Gonzalez said.

The Braves are still interested in adding a left-handed hitter for the bench and possibly more pitching, but might wait until August, after Wednesday’s non-waiver trade deadline. Before giving up young talent in another potential trade, they might wait to see how the team performs after some players return from the disabled list.

“It’s been a busy day,” general manager Frank Wren said Monday afternoon. “We’ve had a lot of conversations and I don’t know if anything will come to fruition, but we’ve had a lot of conversations on different fronts. You continue to knock on doors and make calls until you feel like you’ve exhausted all the possibilities to improve your team.”

Bolstering the bullpen was a priority before Wednesday’s deadline and became more so after the Braves lost veteran starter and staff leader Tim Hudson to a season-ending broken ankle Wednesday.

With the trade price set so high for the few front-line starters available, the Braves opted to make their bullpen more formidable.

“Three years ago when he was acquired as a free agent by Anaheim, he was one of the best left-handed relievers in the game and he’s a guy you trust,” Wren said of Downs. “That’s a big word for us. You’re getting late in the game in the bullpen, you want somebody out there you trust. He personifies that.”

Downs had a 1.24 ERA before his last appearance Thursday at Oakland, where he gave up two runs and three hits, including his only homer allowed this season.

“Anything we can get to help the team make the playoffs and get us farther in the playoffs, that is going to be great for us,” Avilan said. “It’s really good having another lefty in the bullpen, especially him. Walden told me he’s a really good pitcher, really good against lefty hitters, so that’s going to be good for the team.”

Entering Tuesday play, Atlanta’s bullpen ERA was a majors-best 2.62, ahead of the Pirates (2.84) and Royals (2.95). Atlanta and Pittsburgh relievers are tied for lowest opponents’ average at .214.

Downs had a .183 opponents’ average over 29 appearances through July 23. The Kentucky native’s 2.28 ERA since the beginning of the 2008 season ranks fourth among major league relievers (minimum 200 innings).

Rasmus, 25, had a 1.72 ERA and 14 saves in 32 appearances for Triple-A Gwinnett, with 48 strikeouts and 22 walks in 36 2/3 innings. He struggled in three appearances with Atlanta this season, allowing eight hits, six earned runs, four homers and three walks in 6 2/3 innings.

He was 17-22 with a 3.61 ERA in 143 games (35 starts) in seven minor league seasons.

Downs has compiled a 36-35 record and 3.47 ERA in 539 games (50 starts) over 12 seasons with the Cubs, Expos, Blue Jays and Angels. He had a career-best 1.34 ERA in 60 appearances for the Angels in 2011.