BINGHAMTON, N.Y. — Just when Portland started letting the benefits of a fast start get away, a reinforcement helped return the Sea Dogs to their winning ways.

Brian Johnson made an impressive Double-A debut Saturday to help the Sea Dogs down the Binghamton Mets 9-3, earning a split of a doubleheader and stopping a three-game Eastern League losing streak.

The Sea Dogs (16-10) lost the Eastern Division lead Friday night to the Trenton Thunder, then dropped Saturday’s first game, 3-2.

Johnson, a 23-year-old left-hander who was picked 31st overall in the 2012 draft, did not allow an earned run in 51/3 innings while the offense snapped out of a brief slump.

The Sea Dogs had managed just four runs in the three losses. In Saturday’s second game, they had two four-run innings.

“It was nice to get back on track,” said first baseman Travis Shaw, who went 3 for 4 and scored twice while pushing his batting average above .300. “With how we had been playing, it felt like we hadn’t won in a long time.

“Brian Johnson pitched outstanding today for his first game at Double-A.”

Shannon Wilkerson tripled home two runs in the four-run second inning, which started the scoring. Deven Marrero and Carlos Rivero sandwiched homers around a Shaw single to start the fifth as the Sea Dogs added four more runs to increase their lead from 5-1 to 9-1.

That was more than enough for Johnson.

Pitching at the Double-A level earlier than he had expected, Johnson gave up just three singles and did not walk a batter. Counting six perfect innings in one game for the Salem Red Sox in the High-A Carolina League, Johnson has not given up an earned run in three starts. He has allowed just seven hits and one walk while striking out 16 in 171/3 innings during that stretch.

“I had command of my fastball and was getting strike one,” said Johnson, who credited catcher Matt Spring and pitching coach Bob Kipper with leading him through his debut.

Sea Dogs Manager Billy McMillon confirmed that the move was a promotion for Johnson, rather than filling a temporary hole. The third-year pro who was a two-time all-SEC selection at Florida appeared ready.

“He did a really good job for us,” McMillon said. “He mixed up his pitches well.”

Johnson was drafted with the sandwich pick that was compensation for Boston losing Jonathan Papelbon to free agency. He is 4-1 this season and has a 2.59 ERA through 29 pro starts.

Henry Ramos helped fuel the 13-hit support for Johnson, providing a single, a double, a run and an RBI.

In the opener, Henry Owens (3-2) worked all six innings, allowing six hits, but his wildness allowed the Mets to win 3-2.

Matt Clark was hit by a pitch in the sixth inning and scored the winning run on a wild pitch.

Shaw, who drove in both runs, and Mookie Betts had two hits each for the Sea Dogs.

The Sea Dogs loaded the bases in the seventh inning but could not score.

Betts had a 17-game hitting streak snapped Friday, but bounced back to go 3 for 9 in the doubleheader and is batting a league-high .406.