Kyle Isbel, right, is congratulated by Bobby Witt Jr. after scoring on a single by MJ Melendez during Kansas City’s 13-5 win Sunday over the Boston Red Sox. Colin E. Braley/Associated Press

KANSAS CITY, Mo. — On paper, four games against a lowly Royals team looked like a great opportunity for the Boston Red Sox to pick up some ground in the playoff race. Instead, the weekend can be counted as a missed opportunity.

Jarren Duran had an adventurous day in center field as the Red Sox dropped Sunday’s series finale, 13-5, and ended up losing three of four to the Royals, who even after a good weekend are 44-65.

MJ Melendez’s three-run homer off Kutter Crawford in the fifth inning – which came after Duran couldn’t catch a Nate Eaton fly ball – broke things open, then the Royals added six runs in the eighth inning in a sloppy game played on a brutally hot day at Kauffman Stadium.

Kansas City opened the scoring in the third when Crawford balked, allowing Michael Massey to score. Melendez then made it 2-0 with an RBI single to center.

In the fifth, Massey walked before Eaton lifted a ball to center that Duran could not corral. The next batter, Melendez, broke things open with a three-run shot that put the Royals up 5-0.

Crawford, who entered with a 2.72 ERA dating back to June 12, posted his worst outing in some time. He allowed five earned runs on five hits in five innings while recording four strikeouts.

“Just the command, not having the greatest feel and you fall behind and I just had a hard time getting back into counts,” Crawford said. “They were coming out swinging early.”

Rafael Devers made it 5-1 with a solo shot in the sixth and Tommy Pham brought the Sox back within two runs with a two-run, 437-foot blast to left field in the seventh. In the bottom of the inning, Duran’s struggles really hurt his team.

Leading off, Eaton lifted a routine fly ball to center that Duran lost in the sun, allowing Eaton to advance to third for a triple. The next batter, Kyle Isbel, hit a deep fly ball that glanced off Duran’s glove on the warning track and went for an RBI triple. A Melendez sacrifice fly – on a Duran diving catch – made it 7-3. Duran then got into a dispute with fans in the bleachers and had to be momentarily held back by left fielder Alex Verdugo. Once Duran got back to the dugout, Manager Alex Cora sat next to him on the bench and appeared to try to console him.

In a postgame interview, Cora ignored Duran’s mistakes other than the ball he lost in the sun.

“Been there done that,” Cora said on NESN. “You try to get the angle, you saw that right away. The only thing is, it’s not urgency, but it’s like, when you are in danger, you scream for help so your teammates go to help him. But there’s nothing he can do there. He turned around and put his hand up and didn’t catch it.”

Duran ranks as one of the worst center fielders in the big leagues, entering Sunday with minus-six defensive runs saved compared to an average defender. But with Kiké Hernandez still on the injured list and Jackie Bradley Jr. no longer on the roster, Cora is committed to Duran.

“He’s our center fielder right now,” he said on NESN. “We trust him. This is a kid that’s part of what we’re trying to accomplish and we’re going to keep rolling with him.”

Kansas City really broke things open in the eighth with a six-run inning. Darwinzon Hernandez entered in relief and walked four batters, including the first three he faced. After Massey made it 9-3 with a two-run single, Isbel hit a two-run double off Austin Davis. A Melendez sacrifice fly – his sixth RBI of the day – made it 12-3, and Bobby Witt Jr. added an RBI single.

With the loss, the Red Sox fell to 54-56. They have lost four of six after a three-game winning streak and finished their road trip at 3-4. Boston is 10-21 in its last 31 games.