ARLINGTON, Texas (AP) — The Los Angeles Dodgers are having trouble figuring out the back end of their bullpen. Blake Treinen surrendered Austin Riley's tiebreaking home run leading off the ninth inning, and the right-hander combined with lefty Jake McGee to give up four runs in Atlanta's 5-1 victory over the Dodgers in the NL Championship Series opener Monday night. Treinen and McGee were two of the ninth-inning options because Kenley Jansen, the club's career leader in saves, has been struggling with his velocity and command. Manager Dave Roberts has chosen his words carefully while saying the bullpen roles are open in the ninth. Ronald Acuña Jr. followed Riley's homer with a double, and Treinen was gone after giving up Marcell Ozuna's RBI single. Treinen's only out was a long flyball to center by Freddie Freeman that moved Ozuna to third. After starter Walker Buehler allowed one run with seven strikeouts in five innings, Brusdar Graterol retired three straight to escape the sixth when he replaced Buehler after consecutive singles from Travis d'Árnaud and Albies to start the inning. Dustin May and Víctor González combined for two scoreless innings before Treinen came on. Buehler, who’s been dealing with a blister, came out after 100 pitches and a career-high five walks. “It’s hard to say you’re too fine," he said. "I feel like I’ve been decently successful. I don’t want to walk guys. We’re trying to keep runs off the board. I can go deeper. I can be better.” Baseball's highest-scoring offense was no match for the hottest playoff pitching staff either. The Dodgers didn't have a baserunner over the final four innings as their last 13 hitters were retired. The last to reach was Corey Seager via single, three batters after Kiké Hernández's solo home run leading off the fifth. Atlanta was the first team since the 1905 New York Giants to record four shutouts in the first five games in the same postseason. ___ More AP MLB: https://apnews.com/MLB and https://twitter.com/AP_Sports