SAN FRANCISCO -- The Reds started off on the wrong foot right from the first pitch of Sunday's series finale at Oracle Park.

Leadoff hitter TJ Friedl stepped into the box against Giants left-hander Kyle Harrison and immediately took a 90.6 mph four-seamer off his left thumb. Friedl doubled over in apparent pain and cradled his hand, staying down for a while before getting up and walking to first base with a trainer.

Following a lengthy discussion, Friedl initially stayed in the game, swiping second base and advancing to third on an errant throw before eventually scoring on Jeimer Candelario's bases-clearing double. But when the inning flipped, Friedl was out of the game, with Stuart Fairchild sliding over to center in his place and Will Benson entering the game to play right field.

"The nail was really bruised up," Friedl said after the Reds' 6-5 walk-off loss in 10 innings. "We just wanted to get it taken care of and just kind of examine it and see what was going on instead of going back in. We just took the time to ice it down and ¡­ start the healing process a little."

Friedl was playing in his sixth game of the 2024 campaign after missing the beginning of the season with a fractured right wrist.

X-rays on Friedl's thumb came back inconclusive, per the team, and he will see a hand specialist in Arizona to get additional imaging done, making him likely unavailable for Monday's series opener against the D-backs.

Because the ball hit him high up on the thumb, Friedl thinks the bulk of the damage might be limited to bruising around his nail bed and fingertip, which pinched into the bat when he was struck.

"I could bend it down and then extend it up," Friedl said of the mobility in his thumb, which was bandaged after the game. "It's just so swollen that the movement was minimal."

With Friedl's injury hanging overhead, the Reds had to stomach their fifth consecutive series loss. Cincinnati managed to score more than four runs for the first time in 10 games, but the team could not come all the way back from San Francisco's five-spot in the fifth inning.

Reds starter Frankie Montas had put up four scoreless frames to open his second start back from the injured list, but he unraveled afterward. He allowed an RBI single to Matt Chapman, two-run shot to LaMonte Wade Jr. that would only have gone out at Oracle Park, according to Statcast, and an RBI single to Heliot Ramos before departing with two outs in the fifth inning.

Nick Martinez then entered and surrendered a single to Blake Sabol, with Ramos scoring an unearned run due to Elly De La Cruz's throwing error on the play.

The Reds cut the Giants' lead to one run on Jake Fraley's pinch-hit RBI single in the seventh and tied the game at 5 on Mike Ford's solo homer -- his first with Cincinnati -- in the eighth. But in both the ninth and 10th innings, they could not cash in with two runners in scoring position and two outs.

In all, the Reds went 2-for-12 with runners in scoring position and stranded 13 on Sunday.

"We had some opportunities to try to score some runs; we just couldn't come up with a big hit," said bench coach Freddie Benavides, who stepped in when manager David Bell had to leave the dugout mid-game to deal with stomach issues. "Credit to their pitching staff, of course. ¡­ I thought some of the guys swung the bat pretty good in general, and then the balls just didn't fall."

While the big hits didn't fall for the Reds, the Giants' Casey Schmitt crushed an RBI double to left field for the walk-off knock, his first hit of the season.

Cincinnati ended its season-high eight-game skid in Friday's series opener, but the team has lost 10 of its last 11 and plated just 27 runs in that span.

The Reds, who are now a season-high six games under .500, believe they are a better team than they have been in the first month and a half of 2024.

"The only thing we can do is just keep going out there and keep on grinding," Montas said. "It's not going to be [like this] the whole season. ¡­ We are working to get out of this, and like I said, that's the only thing that we can control."