The Padres’ 5-4 loss in San Francisco on Friday night was a particularly painful one -- and not merely because Blake Snell struggled and the team missed out on its chance to leapfrog the Giants into first place in the National League West.

Catcher Austin Nola and right-hander Keone Kela -- both of whom had spent time on the injured list already this season -- exited the game with injuries. Nola was diagnosed with a left-hand contusion, though X-rays were negative, and he could return to the lineup soon, manager Jayce Tingler said.

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The prognosis on Kela, who exited with forearm tightness in the seventh, seems a bit murkier. Kela surrendered a go-ahead home run to Austin Slater, which proved to be the game’s decisive moment. He was promptly visited by a team trainer, with his fastball sitting in the low 90s, well below its typical velocity.

“It just tightened up on him somewhere during the at-bat,” Tingler said. “We’ll wait and see what [the doctors] say.”

Kela’s signing was always a bit of a risk, after he’d pitched just two innings last season because of inflammation in his right forearm. The Padres felt it was a risk worth taking because of his track record. Kela owns a 3.29 ERA across seven big league seasons and was headed for a prominent role in the San Diego ‘pen before the injury bug bit. Still, despite a flurry of injuries, the Padres deep relief corps has managed a 2.72 ERA this season -- the best mark in the National League.

The catching situation isn’t quite as stable, making for a major sigh of relief with Nola’s negative X-ray. The left hand is a particularly precarious spot for Nola -- who missed the first four weeks of the season with a broken middle finger on that hand. The hit-by-pitch on Friday appeared to miss Nola's finger -- but only barely, as Nola quickly developed a large bruise on the back side of his hand. Tingler said the pitch broke a blood vessel, causing additional swelling.

The Padres sorely missed Nola while he opened the season on the injured list. He's one of the sport's best-hitting catchers -- he posted a .273/.353/.472 slash line last season -- and a strong defender, too. It was always doubtful that Nola would start on Saturday -- a day game after a night game, with Joe Musgrove on the mound. (Victor Caratini has caught every one of Musgrove’s starts this season.) But Tingler seemed optimistic that Nola would be available off the bench.

Before his early exit, Nola backstopped a bizarre outing from Snell. Snell’s stuff remains electric, and he allowed just one hit -- a Buster Posey two-run homer in the third inning. But his control eluded him entirely. The left-hander walked six Giants and exited after just 4 2/3 innings, allowing four runs.

For Snell, it was a continuation of his somewhat rocky start to his Padres tenure. He has yet to complete six innings in San Diego, and although he’s rarely been hit hard, he simply hasn’t been in the strike zone enough.

“Trying to do too much maybe,” Snell said. “I feel good, so it’s got to be just me overthinking it, because the ball’s coming out good. They’re not hitting the ball. It’s me walking ‘em, deep counts -- it’s pretty self-explanatory. I just need to start making better pitches.”

The way Snell tells it, his pitches feel good, and his mechanics -- while not quite flawless -- aren’t the issue. He says his struggles are mental.

“The biggest thing for me is just to breathe, not get too hard on myself in this moment” Snell said. “Just breathe and stop pressing so hard. We’re a month in, and I haven’t pitched like myself.”

After Snell’s early exit, the Padres stormed back, tying the game at 4 with two-run homers from Trent Grisham and Eric Hosmer in the sixth. But Slater put the Giants on top for good an inning later, and the game ended when pinch-hitter Ha-Seong Kim struck out looking at a 3-2 fastball that appeared to be high and inside.

“I thought it was a bad call,” Tingler said. “I don’t get it. That shouldn’t happen up here. I thought the ball was inside and up. Posey caught it and pulled it back. I just don’t think that should happen. It feels like that’s happened to Kim several times.

“Our guys do a very good job of commanding the zone, and you hate to see a game end that way.”

A night that began with the Padres looking to move into first place ended in frustration -- on multiple fronts.