The Boston Red Sox and Kansas City Royals both played doubleheaders on Monday. For the two American League Wild Card rivals, the day represented an opportunity to gain ground or at least hold steady in the standings.

More than anything, it was an opportunity for the two clubs to show us who they really are, and by day’s end only one looked like a deserving playoff team — and it wasn’t the Red Sox.

The Red Sox were swept in Monday’s doubleheader, losing the suspended game from June 26 by a score of 4-1 before dropping the nightcap 7-3. Jarren Duran continued his brilliance at the plate, going 3 for 4 with a two-run home run and two doubles in the second game, but the Red Sox committed four errors as a team and were doomed by a five-run fifth inning.

Boston has now lost five games in four days, and with the Royals sweeping their doubleheader against Cleveland the club now trail Kansas City by six games in the standings.

The Red Sox started right-handed reliever Zack Kelly, but rather than just have him go one or two innings like a typical opener, the club pushed him harder than he’s ever been pushed in his big league career. Yet Kelly was up for the task, and after two perfect innings he came back out and worked around two walks to finish his outing strong with a scoreless third.

All told Kelly threw a career-high 49 pitches and tied his career-high with three innings.

It wound up being a short but eventful day for Wilyer Abreu as well. The Red Sox rookie struck out in his first at bat, swinging at a pitch low and inside that wound up hitting him right on the toe. He remained in the game and made a slick sliding catch in right field to end the second inning, but when he came to bat again in the bottom of the third he struck out again and was tossed after making a comment to home plate umpire Paul Clemons.

The Red Sox got on the board immediately afterwards when Triston Casas scored Duran with an RBI single, and in the top of the fourth Justin Slaten made his return from the injured list and threw a scoreless frame in his first appearance since July 7.

But then Alex Cora handed the ball to right-hander Brad Keller, and things immediately went off the rails.

Keller, who was called up from Triple-A earlier in the day, got crushed by the Blue Jays batters. He allowed five runs in the fifth inning, allowing seven baserunners on the inning including two doubles and a three-run home run by George Springer.

Springer’s liner, which curled around Pesky’s Pole down the right field line, put Toronto up 3-1 and things quickly snowballed when Rob Refsnyder misplayed a fly ball in left, allowing Joey Loperfido to reach on a two-base error. Addison Barger hit an RBI single and Ernie Clement an RBI double to round out the inning before Keller finally struck out David Schneider to end the inning after 10 batters.

Keller ultimately threw four innings of bulk relief, settling down to keep things scoreless the remainder of his outing. Duran hit a two-run home run in the bottom of the eighth to cut the deficit to 5-3, and with 19 home runs on the season he is now one homer away from becoming just the third player in Red Sox history to record 20 home runs and 30 stolen bases in a single season.

Unfortunately that was as close as the Red Sox could get. Right-hander Chris Martin came on in the top of the ninth and allowed two runs to make it 7-3, and Boston never threatened again after that.