SANTA CLARA, Calif. -- The San Francisco 49ers breathed a collective sigh of relief Monday after receiving important injury news on two of their best players.

Niners coach Kyle Shanahan said Monday that receiver Deebo Samuel and linebacker Fred Warner suffered groin and hamstring strains, respectively, in San Francisco's 34-26 victory Sunday over the Minnesota Vikings.

The bad news is that both will miss at least Sunday's game against the Seattle Seahawks. But Shanahan was more pleased by the fact that both players aren't expected to miss more than a game or two as the 6-5 Niners make their push for an NFC playoff spot.

"That's what I was kind of telling you guys last night that I hope for that it was just a strain," Shanahan said. "And strains usually [last] anywhere from one to two weeks. I think it was very good news considering what it could have been."

According to Shanahan, both Samuel and Warner could return as soon as the Dec. 12 game against the Cincinnati Bengals. Barring a setback, both would be expected back in time for a Dec. 19 home game against the Atlanta Falcons.

While the Niners got relatively good news in the big picture, the loss of Samuel and Warner even for one week is significant.

Samuel has been the team's most productive offensive player, establishing himself as the league's premier multidimensional weapon.

On Sunday, Samuel became just the third player in NFL history to record 1,000 receiving yards, five rushing touchdowns and five receiving scores in the same season.

Without Samuel, the Niners will look to second-year receiver Brandon Aiyuk to continue building on his recent surge, as well as the likes of tight end George Kittle, wideout Jauan Jennings and a burgeoning running game.

"He's been a big part of our offense," Shanahan said. "But I think we're in a spot right now that we can overcome that."

Replacing Warner also won't be easy, especially since it's something the Niners haven't had to do at any point in his three-plus seasons. When he misses Sunday's game against the Seahawks, it will be the first contest Warner has missed since he came into the league in 2018, snapping a streak of 59 consecutive regular-season starts.

When Warner departed in the third quarter against the Vikings, the Niners turned to Demetrius Flannigan-Fowles to step in at middle linebacker with Azeez Al-Shaair remaining at weakside linebacker.

How that plays out this week will depend on the status of fellow linebacker Dre Greenlaw. Greenlaw also left Sunday's game with what Shanahan described as an "irritation" of the core muscle injury that had kept him out since Week 1. Greenlaw is considered day-to-day this week.

And with strongside linebacker Marcell Harris in the concussion protocol, the 49ers figure to enter the Seattle game woefully thin at linebacker. That puts even more onus on Al-Shaair, who had an interception and a fumble recovery in the win against Minnesota.

"Azeez has been ready for anything we've asked him to do," Shanahan said. "He always runs around and plays like his hair is on fire and he loves playing the football game. That's not changing, but he's just getting more and more confident of where to be, what to anticipate ... He's been playing at a high level all year and whether he's inside or outside, I expect it to continue, we need it to continue, because he's one of the reasons we're playing pretty good right now."

Elsewhere on the injury front, running back Trey Sermon suffered an ankle sprain that Shanahan said will keep him out "for a little while" and makes him a candidate to head to injured reserve with a chance to return later in the season.