One reason the Portland Sea Dogs are dominating in the Eastern League is pitching, leading the league with a .358 ERA.

The arms came through again Saturday as the Sea Dogs swept the New Britain Rock Cats 4-0 and 4-2, before a sold-out Hadlock Field crowd of 7,368.

Mike McCarthy (8-3) pitched five scoreless innings in the first game, while Luis Diaz (3-1) threw a complete-game (seven innings) five-hitter, allowing two runs.

Second baseman Sean Coyle paced the offense with five RBI, including his team-leading 11th home run.

The Sea Dogs improved to 58-29, the best record among all Triple-A and Double-A teams. The Rock Cats dropped to 42-42.

While Diaz is emerging as a prospect (now with a 2.00 ERA in four Double-A starts), McCarthy plays one of those valuable pitching roles on a baseball team. Just plug him in where you need him.

McCarthy, 26, a long reliever and spot starter, has actually made more starts (10) than relief appearances (seven). He is filling in for Keith Couch, who just went on the disabled list.

“Frankly (relief) is my role. But whatever I can do to help the team win,” McCarthy said. “If they need me to close, if they need me to start, if they need me to play shortstop, just let me know and I’m out there.

“It’s a unique situation, but I think it’s a valuable one. It gives me a lot of versatility in my career.”

McCarthy’s ERA is 4.42, although he has only four outings where he gave up more than three runs.

“I have to continue to be effective with my pitches and stay down in the zone,” he said. “In a couple outings I didn’t do that.”

He did Saturday, giving up three hits and striking out five. Only one out was recorded in the air – a fly ball to foul territory in right.

In the first game, New Britain started Virgil Vasquez, 32, a former major leaguer with the Tigers.

Leadoff batter Derrik Gibson greeted Vasquez (4-5) with a double. He moved to third on a single by Shannon Wilkerson and scored on Coyle’s sacrifice fly.

In the fourth, David Chester doubled in Michael Almanzar. Later, with bases loaded, Wilkerson singled in two.

Robby Scott relieved McCarthy and pitched two scoreless innings for his second save, dropping his ERA to 1.34.

Diaz utilized a mix of fastballs (88 to 94 mph), change-ups and curveballs. He got 13 swings and misses, striking out six, walking one.

Coyle crushed a two-run homer in the first inning, and then singled in two in the second.

NOTES: McCarthy’s eight wins is tied for third in the league. Henry Owens (11-3) leads the league … Some media reports had major league utility player Mike Carp coming to Portland for a rehab appearance. But Carp flew to Syracuse to join Triple-A Pawtucket, where he homered Saturday … The Sea Dogs play Sunday at 1 p.m. before heading to Binghamton for a four-game series.