BOSTON -- Things could not have started out much better for the A’s on Monday night. But sometimes, one play can change the entire momentum of a game, and that was certainly the case in Oakland's 9-4 loss to the Red Sox at Fenway Park.

Second baseman Jurickson Profar's struggles with seemingly routine throws have been well-documented this season. His errors have often come in critical situations, and his errant throw in the third inning against Boston was a backbreaker.

Holding a four-run lead, one which Profar played a huge part in building up with a two-run single the previous inning, starter Frankie Montas induced a ground ball against Tzu-Wei Lin that appeared ticketed straight for Profar to turn an inning-ending double play. It’s a skill Montas has developed this year to emerge as the A’s top starter so far. His 57.8 ground-ball percentage entering the night was tops in the Majors among qualified starters, and he had already gotten out of the first two innings via double plays. But things went awry in his would-be third time doing the same.

“It’s very frustrating, especially for Frankie,” Profar said. “He was having a good game and it got out of hand because of that play.”

As Profar hauled in the hopper from Lin, he appeared to hesitate for a half-second while transferring the ball to his right hand while he tried to get the throw off. When he finally did get rid of the ball, it bounced in the dirt well in front of shortstop Marcus Semien, waiting at second base, and leaked out towards third.

Instead of the inning being over, the Red Sox capitalized on the mistake and put up a six-run inning. Other mistakes were made on defense in that frame, including an error by Montas as he failed to keep his foot on first base while covering the bag for what would have been the second out**,** a play he thought he made.

“I felt like my foot touched the bag,” Montas said. “But there’s nothing I can do to change that.”

Ramón Laureano also took a bad route on a Xander Bogaerts fly ball to center field that turned into a two-run double. But Profar’s costly mistake opened the floodgates.

“It looked like he didn’t get a great handle on it, then tried to hurry the throw,” Oakland manager Bob Melvin said of Profar’s error. “Had a chance to get out of the inning there and it just got out of hand.”

Montas admitted to letting Profar’s error get inside his head on the mound as the inning went along, but he refused to make the second baseman a scapegoat.

“Errors are part of the game,” Montas said. “I still need to stay in the game and make better pitches.”

After pitching into at least the sixth inning in each of his five starts this season, Monday’s outing was Montas' shortest of the year as he was pulled after just 4 1/3 innings. He surrendered seven runs on eight hits while allowing two walks and striking out four, but only one of those runs was earned as the rest followed the disastrous sequence of events in the third. Montas' ERA for the actually dropped from 3.10 to 2.97 after the loss.

“I wasn’t able to hit my spots and make good pitches,” Montas said. “I was a little bit lost and they are pretty good hitters. You have to stay on your game with them.”

Looking for guidance

The error was Profar’s seventh of the year, which leads all Major League second basemen. The A’s are now 2-4 in games in which Profar has made an error.

In an effort to fix his throwing issues, Profar said he spent time talking with Semien after the game. Semien, who has had his own defensive problems in past years, bounced back in 2018 with defense improved enough that he was a Gold Glove finalist at shortstop.

If anyone on Oakland’s team might have a tip or two for Profar on how to navigate these tough times, it would be Semien.

“I talked to Marcus a little bit and he talked to me about what he did, so I’m going to follow his steps,” Profar said. “Try to get better to help my team win.”

Seeing different looks

The A’s did all of their damage on offense in the second by plating four runs in the inning. They managed to chase Red Sox starter Eduardo Rodriguez in the fifth, but Boston’s bullpen held Oakland scoreless over the final 4 1/3 innings.

One hit -- a single by Semien in the ninth off Hector Velázquez -- was all the A’s could muster against six Red Sox relievers.

“It’s just the way the game is now,” Melvin said. “You’re going to see a lot of relievers and they try to give you a different look each time.”

Getting back on track

The loss pushed Oakland’s losing streak to four games, and the club has dropped seven of its last 10.

Even on a tough night like Monday, A’s players are seeing signs that things are starting to come around. Last season, it was not until May that they began their furious run to the 2018 playoffs, and they believe that can be replicated.

“We’re going to jump back on it,” Montas said. “Guys are starting to feel better at the plate. When we get on a roll, we’re going to start winning games.”