But once he arrived, Mortensen was told to go back. Cook had decided to stay in the game.

“That was weird,’’ Mortensen said. “They told me Cookie was going to try and pitch through it and be ready just in case.’’

Cook couldn’t get through the third inning, and Mortensen did come in at that point to face Mark Reynolds with two runners on and two outs.

Reynolds connected on the sixth pitch Mortensen threw, driving it over the wall in left for a three-run homer. That gave the Orioles an 8-0 lead in a game they went on to win, 8-2.

“I tried to sneak a fastball in on him and left it too much over the plate and he put a good swing on it,’’ Mortensen said. “He’s a dangerous hitter. It was a horrible pitch by me.’’

Mortensen allowed two hits over 3 1/3 innings and struck out five without a walk. In two appearances since being called up, he has allowed one run in 6 1/3 innings and struck out 11.

“It’s worked out OK,’’ Mortensen said. “I’ve been able to keep them from getting squared up.’’

Scott Atchison also pitched well, throwing three near-perfect innings. He retired nine of the 10 batters he faced, allowing one walk. Atchison has a 1.50 earned run average in 12 appearances.

“Just trying to throw strikes, get outs, and go from there,’’ Atchison said. “Still early in the year, got a long way to go. But I feel good right now.’’

After using six relievers for eight innings Friday night, Mortensen and Atchison helped save the bullpen for Sunday’s series finale.

After a rough start to the season, the Sox bullpen has given up only six earned runs in its last 41 1/3 innings. That is partly attributable to the relievers settling into roles.

“It’s probably a little more defined now, I guess,’’ manager Bobby Valentine said. “If the game goes a [certain] way, things can fall into place. You definitely have to adjust during games, though.

“There might have been some uncertainty at the beginning of the season. But I thought they pitched pretty well except for about four innings even the first 10 days of the season.’’

Middlebrooks sits

Rookie third baseman Will Middlebrooks, who was 3 for 9 in his first two games, was scratched from the lineup 90 minutes before the game because of a cramp in his left hamstring.

That caused some lineup shuffling. Nick Punto replaced Middlebrooks at third base and hit leadoff. He was 0 for 4 and is now hitting .148.

Valentine originally had Ryan Sweeney hitting first.

Middlebrooks said he worked the cramp out and he would be ready to play Sunday.

“I’ve been drinking a lot of fluids,’’ he said. “I’m fine now.’’

With only three players on the bench, Valentine did not want to take the chance of starting Middlebrooks and losing him to an injury.

Bird watching

The Red Sox are 19-19 against the Orioles since the start of the 2010 season with losses in six of the last seven games and eight of the last 11.

“When you’re playing against teams that are playing good like they are, you better bring your A game,’’ David Ortiz said. “Because they’re not wasting it right now. They’re making plays, their pitchers are pitching well, they’re hitting.’’

The 18-9 Orioles have won four straight and are 10-5 on the road. They are nine games over .500 for the first time since July 15, 2005.

Baltimore starter Jason Hammel held the Sox to two runs over 6 2/3 innings. He has allowed two runs or less in each of his six starts this season.

MRI for Youkilis

Kevin Youkilis had an MRI on his strained lower back. Valentine said he was waiting to hear the results. Youkilis had said Wednesday that he was making progress and that an MRI wouldn’t be needed . . . Carl Crawford still has “thickness’’ in his elbow after receiving an injection of platelet-rich plasma April 26 to help his partially torn ulnar collateral ligament. Crawford is due for an exam later this week and could be cleared to start swinging a bat again.

Back in the swing

Adrian Gonzalez is 6 for 10 in the last two games after snapping an 0-for-18 skid. “I’m feeling better,’’ he said. “I never doubted I would.’’ . . . The Red Sox have gone 43 innings without hitting a home run, the last one coming in the fifth inning last Monday when Mike Aviles connected. This is the first time the Red Sox have not hit a home run in four consecutive games at Fenway Park since May 11-14, 2007 . . . The Sox are 0-4 in May, getting outscored, 23-11 . . . The Sox were 11-15 after 26 games last season and were tied for first by May 30. The difference is they were only five games out last season after 26 games and are 7 1/2 back this season.

Peter Abraham can be reached at pabraham@globe.com. Follow him on Twitter @PeteAbe.