CINCINNATI -- Getting a big rally to expand a lead and then turning a game over to rookie reliever Alexis Díaz has usually meant good things are happening for the Reds. On Saturday afternoon, Díaz saw how fast things can slip away.

Díaz gave up a three-run home run to Juan Soto in the top of the seventh inning, and it was the first three of seven runs to score against the Reds bullpen during a deflating 10-8 loss to the Nationals at Great American Ball Park.

"Obviously it hurts. You want to win every game," said right fielder Albert Almora Jr., whose grand slam in the fifth inning gave Cincinnati a 7-3 lead. "These guys are battling their butts off on the mound. It happens. They’re really good as well. They’ve got some good power hitters. It was one of those games."

All of the Reds' runs up until the ninth inning came via two-out plate appearances with the bases loaded. Kyle Farmer hit a two-run single in the bottom of the first inning for a 2-0 advantage. In the fifth, Mike Moustakas worked a thrilling 11-pitch walk to force home a run and Almora immediately followed Moustakas by hitting his grand slam to left field against reliever Jordan Weems.

"After that emotional inning, you kind of want to find a way to add more runs on and slam the door shut and find a way to get that W," Moustakas said. "Things happen in this game."

Returning for the sixth inning, Reds starting pitcher Tyler Mahle kept Washington at bay with a scoreless frame with two strikeouts. At 104 pitches, he gave way to the bullpen.

Manager David Bell didn't have his full group of relievers available, but his best was at his disposal with plenty of rest in Díaz, who came in with a 1.13 ERA and hadn't allowed a run in 19 of his 22 appearances. He hadn't pitched since Tuesday at Boston.

With one out in the top of the seventh inning, César Hernández scorched a double to right field and Lane Thomas hit a hard single into left field. On a 1-1 fastball, Soto connected with 109.8 mph exit velocity and launched his three-run homer to right field to make it a 7-6 game.

“I was trying to dominate with my best pitch I have, which is the fastball up or above the zone. Unfortunately, that ball just stayed in the middle of the plate, and [Soto] won that battle," Díaz said via translator Jorge Merlos.

Díaz walked his next batter, Nelson Cruz, but got back-to-back strikeouts to end the inning.

"He was on three days' rest. He had been pitching a lot before that," Bell said of Díaz. "Just looked like he had the velocity, he had the life like he always does. Had the break on his breaking ball, but he had a tough time keeping it in the zone, really. It was just, maybe he could have been too strong. We'll have to take a look or just turn the page and move on to the next time. He's been so good all year.”

The Reds bullpen ERA was ranked 28th in the Major Leagues entering the day, but it had improved recently as the rotation began putting together longer starts. Tony Santillan, who had a 2.53 ERA over his last 10 appearances and was also last used on Tuesday, gave up Maikel Franco's one-out single and a wild pitch in the eighth inning before Luis García tied the game with a double to right field.

“Tony looked like he had good stuff," Bell said. "Just again, the slider [and] having trouble throwing strikes with it consistently."

Hunter Strickland opened the top of the ninth inning by allowing a pair of singles, but Franco's two-out RBI single put Washington ahead and García’s two-run single put the game away.

"When we get a lead, our bullpen has done a nice job for the most part," Bell said. "They're going to happen. We had it kind of lined up the way we wanted. It was really just a tough day for a few guys in our bullpen, but for the most part, most times we've been in that situation, we've gotten the job done.”