PHILADELPHIA -- On the verge of a seemingly improbable seven-inning doubleheader sweep, the Nationals' bullpen instead had another final-inning collapse in Thursday's Game 2 loss against the Phillies at Citizens Bank Park.

Hours after the Nats had traded closer Brad Hand to the Blue Jays, Wander Suero, Tanner Rainey and Sam Clay were all unable to shut the door in an 11-8 loss in eight innings. Clay ultimately served up a walk-off grand slam to Brad Miller in the bottom of the eighth as the Nationals suffered their third walk-off loss in their last five games.

• Box score

That came one batter after Clay had walked pitcher Aaron Nola -- called on as a pinch-hitter with the Phillies out of bench players -- to load the bases. Nola had been trying to drop down a bunt with two on and only one out.

“Tough loss. You can't walk guys in a crucial situation,” manager Dave Martinez said. “The walks hurt us. The walk to the pitcher bunting -- for me, that was the big part of that inning right there.”

That brought Martinez out of the dugout -- not to make a pitching change, but to deliver an animated message to his 28-year-old left-hander.

“I just told him, ‘Hey, you’ve got great stuff. Go out there, make your pitches. Get two strikes on him and just make a pitch,’” Martinez said. “He kept throwing sinkers; he threw one down and in, where [Miller’s] really good.”

Though the sinker was actually a bit out of the zone, Miller turned it around for a no-doubt walk-off. It marked the 11th grand slam allowed by the Nationals this season. No other team has allowed more than six.

It was a brutal ending for a team that had endured a wild 48-hour span. It started on Tuesday, when Trea Turner departed in the first inning after testing positive for COVID-19. Wednesday’s game was then postponed after Washington had 13 people (four players, nine staff members) test positive for COVID. That set the stage for another wild sequence on Thursday.

Max Scherzer returned to the mound -- amidst swirling trade rumors -- to toss a gem in the Nationals’ 3-1 victory in Game 1. But with Hand out of the picture, the Nats were once again left searching for bullpen answers following a late-game meltdown in the nightcap.

Though they jumped out to a 7-0 lead in the third inning, that advantage had waned to 7-4 by the time Suero took over in the bottom of the sixth. Tasked with trying to secure a six-out save in Hand's absence, Suero pitched a clean sixth and retired the first two batters in the seventh before allowing a two-out single to Miller and issuing a walk to Andrew McCutchen.

At that point, manager Dave Martinez turned to Tanner Rainey, who had been activated from the injured list prior to Game 1. Making his first appearance since June 27, Rainey allowed an RBI single to Alec Bohm, then walked Ronald Torreyes to load the bases. Phillies catcher J.T. Realmuto tied the game with a two-run single.

“Suero threw the ball really well, he just ran out of gas. I gave the ball to Rainey, and at that moment, he just couldn’t close out the game,” Martinez said. “Unfortunate, but we’ve got to keep going. It’s been a long 24-48 hours, we’ve just got to keep going.”

With Thursday's split, the Nationals (47-55) are 7 1/2 games back of the first-place Mets in the National League East. The team has already traded its closer, and Scherzer could potentially be next as the most-coveted pitcher on the market. And they may not be the only ones to get moved.

“It’s a lot. The whole COVID situation, Brad being traded today, things going on -- it’s definitely weird,” said Josh Harrison, who racked up three doubles and a home run across the doubleheader. “But at the same time, I’ve been in this situation before -- not with COVID and everything -- but Trade Deadline, you know what to expect. Things are going to be hectic until that last minute. You’ve got to come out and try to win every ballgame.”