Again, the Orioles looked defeated. Down by four runs, and watching Ryan Zimmerman hit, an unlikely comeback began.

By the time it was over, Chris Tillman’s awful night was forgotten and the loudest crowd of the season at Oriole Park was cheering its head off.

Down by 6-2, Nick Markakis hit his sixth home run of the season to lead off the sixth, and by the time the next inning was over, the Orioles had a three-run lead on their way to a 9-6 win over the Nationals before 39,129.

Chris Davis hit two more home runs, and he has a major league leading 19th. His two-run homer capped off a six-run seventh.

Steve Pearce’s two-run homer off Jordan Zimmermann (8-3) started the uproar. Nate McLouth singled and Manny Machado doubled to tie the score at 6. After Tyler Clippard relieved Zimmermann, Markakis’ RBI single gave the Orioles a 7-6 lead.

Two batters later, Davis, who was celebrated with “Crush Davis” T-shirts given to fans, slammed a two-run shot, and the Orioles led 9-6.

Steve Johnson (1-1) rescued Tillman, who allowed four home runs, three to Zimmerman and one to Roger Bernadina in 4 2/3 innings.

Tommy Hunter worked a perfect eighth. Jim Johnson rebounded from his four-run meltdown to retire all three batters in the ninth and pick up his 16th save.

For the sixth time in seven games, an Orioles starter failed to complete six innings, and for the second straight night, didn’t make it through five.

Zimmerman, who had three homers in his first 137 at-bats, homered off the railing in front of the Nationals’ bullpen in left-center field in the first. After Bernadina hit his second home run in as many nights in the fourth, one that landed on Eutaw Street, Zimmerman followed with his fifth of the year, and the Nationals (27-26) led 4-1.