The Brazilian has missed the matchday squad for the Reds’ 36th game of the Premier League campaign, having been pictured with strapping on his right thigh.
But with a trip to Barcelona to come in the Champions League on Tuesday night, and Liverpool needing to win every game between now and the end of the season, concerns are undoubtedly high.
Speaking ahead of kickoff at Anfield, Klopp insisted it was “not a big thing,” but is clearly not willing to risk Firmino ahead of more challenging clashes.
“Actually, yesterday after training he mentioned a little muscle issue,” the manager told Sky Sports.
“We assess it obviously. It’s not a big thing but was enough to leave him out today, that’s all.”
It has been suggested the issue is with Firmino’s groin, though there is no confirmation at this stage, while JOE’s Melissa Reddy reports it as a slight strain.
The 27-year-old has played in all but one other game for the Reds this season, with a minor ankle injury keeping him out of the 5-0 thrashing of Watford in February.
Meanwhile, Klopp expressed his delight at the “unbelievable” return of Oxlade-Chamberlain, after a year and two days out of the side.
“We had to think about when we wrote the names on the teamsheet today how we call him,” he joked.
“Alex Oxlade-Chamberlain, there are a lot of options obviously—Alex, Ox, Chambo, whatever! It’s that long ago.
“It’s really nice, it’s really good news that he’s back. He has been back for a while and now today back in the squad, so it’s cool—really cool.”