SEATTLE -- Although second-year closer Edwin Diaz hasn't been as dominant as he was his rookie season, Mariners manager Scott Servais expressed confidence Sunday in the 23-year-old again after Diaz took the loss in Saturday's 4-3 setback to the A's.

Diaz is 2-4 with a 3.53 ERA with 13 saves in 16 chances this season. He had a 2.79 ERA and 18 saves in 21 chances last season. His strikeout rate has dropped from 15.3 to 12.1 per nine innings this year while his walk rate has increased from 2.6 to 4.0 per nine innings. He's also allowed eight home runs in 35 2/3 innings after allowing five in 51 2/3 innings a year ago.

But the Mariners are set up to have Diaz close and Servais isn't ready to change that, and he got a 1-2-3 ninth with a pair of strikeouts from the youngster to close out Sunday's 4-0 win over the A's to wrap up the first half.

"Eddie bounced back pretty quick," Servais said prior to Sunday's first-half finale with the A's. "He's a very confident guy and he should be. He's got a great arm and good stuff. When it hasn't gone well, it's more pitch execution and selection.

"In the role you're in, pitching in the ninth inning like that, every little mistake gets magnified and you have no chance or just a brief chance to come back with just three outs to play with. Your room for error is not as big. But he's a confident guy. I talked to him after the game last night and he understands. He said he just didn't get the ball where he wanted it. It's happened to him a few times this year."

Steve Cishek has had previous closing experience and Nick Vincent has pitched well this year, but for now the Mariners will stay on course with Diaz.

"If we get [to the ninth] with a one-run lead or tie game, he's going to be in there again," Servais said. "It's just the way we're set up right now."

Gamel could see some time at first

Servais says Danny Valencia's play at first base has been one of the pleasant first-half surprises as he's done well in an everyday role defensively after the club demoted Daniel Vogelbach and abandoned the initial platoon plan.

But the club would like a back-up option and a left-handed hitter to counter Valencia, and outfielder Ben Gamel continues to do pregame work at first base and could see some time there in the future.

"He's getting much more comfortable working out over there," Servais said. "It's something we may look at in the second half, just firing him over there. It's not ideal, having not played there. He's got one inning in this year. But there might be a day we just have to do it and just roll with it. I think once we get in the second half, we'll take a look at that."

Rotation set coming out of break

Servais said the plan is for James Paxton to pitch the first game after the All-Star break on Friday in Chicago against the White Sox, followed by Felix Hernandez and rookie Andrew Moore . That sets up Ariel Miranda to face the Astros on Monday in Houston, with Sam Gaviglio expected to be recalled from Triple-A Tacoma to pitch the second game with Paxton coming back to close out that series.

Miranda is the only Mariner to make every start this season and leads the club with 104 innings, but Servais said he's not worried about any sort of innings count with the 27-year-old or anyone else in the rotation at this point.

"There's a number of different reasons for [pushing Miranda back to the fourth game out of the break], but that's the way we're going," Servais said. "Miranda, of all the guys this year, has probably been the nicest surprise. He threw the ball well last year for us, but stepping in and taking it and running with it, he's been pretty consistent for the most part and has had a lot of great outings."

Greg Johns has covered the Mariners since 1997, and for MLB.com since 2011. Follow him on Twitter [ @GregJohnsMLB]().