BOSTON -- There are ups and downs to a rookie’s season, and that was evident in Erik Swanson's outing on Friday against the Red Sox.

Just five days after he dazzled in his first career win over the Indians, Swanson was hit hard by the defending World Series Champions in the Mariners' 14-1 loss.

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“It is a learning process for him,” said acting manager Manny Acta, who is filling in for the first two games of the series while Scott Servais attends his daughter’s college graduation. “We like him a lot. He had good stuff at the beginning, but they caught up to him.”

Swanson gave up seven hits, seven runs (including two home runs) and struck out four over 4 2/3 innings at Fenway Park. Mitch Moreland belted a 436-foot three-run homer in the third, according to Statcast, and Rafael Devers followed up in the next inning with a 397-foot solo shot.

“Most teams are going to do their homework,” Swanson said. “They’re going to know that I’m aggressive with my fastball, they know I’m going to go right at them. A couple different times [I was] maybe not quite locating where I wanted to, and guys were able to put the bat to the ball and get in play.”

Swanson (1-4, 6.35 ERA) began the game strong with two hitless innings. When he faced the order for a second time, the hits and homers began adding up. The Mariners trailed, 4-0, by the end of the third.

“He came out of the gate today really good,” Acta said. “He had the fastball. But this is ‘The Show.’ These guys are really good. The second time around, he was not able to locate that fastball or his secondary stuff. They made him pay for it.”

The 25-year-old’s performance was a contrast to his last start on Sunday, when he allowed only one hit and held the Indians scoreless over six innings. Swanson also struck out three that day, propelling the Mariners to a 10-0 team shutout.

Swanson, who threw strikes on 54 of his 81 pitches, noted the differences between Friday’s loss and his most recent win.

“Not being able to put guys away with two strikes, bottom line,” he said. “Especially with my changeup tonight, there were a couple ones that were borderline that caught a little bit too much of the plate, and I just need to get them down a little bit more.”

The 2019 season -- and the experience of playing in the big leagues -- is still young for Swanson. He made his Major League debut out of the bullpen on April 11. Swanson earned his inaugural start on April 17, and became the first pitcher in Mariners’ history to not issue a walk in each of his first three career starts.

“[I will] take exactly what I’m talking about out of this game, move forward and make the adjustments so it doesn’t happen again,” Swanson said.