Jordan Walden was doing nothing more than running as part of a pregame conditioning workout Saturday in St. Louis when he felt tightness in his right groin, and to a lesser extent his left groin.

The Braves reliever hadn’t pitched in a game since. In fact, before Thursday he had last pitched Aug. 21 at New York, when he overpowered Mets hitters with four strikeouts in two perfect innings.

“My groins just tightened up on me,” said Walden, using the plural for an injury that is usually singular, as in one groin muscle or the other. “My right one mainly. Just a hot day, running, it just got me.”

Walden received treatment all week and said his condition improved every day. He threw a light bullpen session Wednesday without incident and planned to throw again Thursday, after which manager Fredi Gonzalez would talk with pitching coach Roger McDowell to see if Walden was ready to pitch.

The hard-throwing setup man had posted a 1.47 ERA and .133 opponents’ average in his last 32 appearances before the injury, with 36 strikeouts and 10 walks in 30-2/3 innings.

He has pitched all season while managing a situation with a bulging disk in his back, which caused him to miss much of spring training. Walden had a 15-day disabled list for a strained shoulder, but had been injury-free since.

“He came in the third day (of the four-game series at St. Louis) and said he was hurting,” Gonzalez said. “Those might have been the best two innings he’s thrown or anybody has thrown. It was nails. We’ve done a good job not using him three days in a row. This is just legs. You could see it with his delivery sometimes he gets so up in the air. He told us it was just from doing the conditioning.”

The Braves have tried to avoid overworking their key relievers this season, and for most of the season they had no pitcher among the National League’s top dozen in number of appearances. But lefty setup man Luis Avilan had pitched in 20 of 37 Braves games since the All-Star break to move into a tie for ninth in the NL with 63 appearances.

Avilan, after allowing only 11 hits (.106 opponents’ average) and no earned runs in 31-2/3 innings over 35 appearances through August 14, gave up seven hits and three earned runs in his past seven appearances before Thursday. That included five hits and two earned runs in 2-2/3 innings of three appearances over the last four days.