Liverpool coach Jurgen Klopp has admitted his concern after James Milner limped off the pitch during the first half of Liverpool's Merseyside derby clash with Everton, while Joel Matip was forced out due to an injury later in the match.
The Reds were forced to make a change when the 34-year-old pulled up with a suspected hamstring injury just before half-time at Goodison Park.
Milner was making the 535th Premier League outing of his career on Saturday, which saw him draw level with Welsh legend Gary Speed in fifth in the top-flight's all-time list of appearances.
Joe Gomez was sent on as a like-for-like replacement for a fellow England international at left-back, as the Reds push for a win which would see them move to within three points of the Premier League title.
During the second half, it was Matip who was forced out of the match with an apparent toe injury, with the defender replaced by Dejan Lovren for Liverpool's fifth and final substitute of the day.
Reds boss Klopp revealed he has worries over Milner and Matip ahead of Wednesday's home clash against Crystal Palace.
"'Millie' felt a hamstring a little bit, but we had this in the past. 'Millie' is not often injured and hopefully it is not serious," the Liverpool manager told a news conference.
"He is smart enough to show up in the moment when he feels it, so hopefully it was the right moment. Maybe not Wednesday [against Palace], but after that I would hope for.
"Joel was unlucky and we had to make a quick decision. It was a situation with Richarlison and he bent or stretched his big toe.
"I don't think a lot of people have had that. It is really painful, but hopefully it settles, the pain settles and then we will see. I hope nothing serious has happened, but I don't know yet."
Liverpool haven't won the league in 30 years, but 27 wins from their first 29 fixtures put them in pole position before the coronavirus stopped play in March.
Klopp's men will increase their lead over reigning champions Manchester City back to 25 points at the summit if they beat their local rivals, but they weren't at their brilliant best in the first half.
Neither side was able to carve out any clear goalscoring chances in a match staged behind closed doors due to the continued threat of coronavirus.
The last four Merseyside derby encounters to take place at Goodison have been goalless at the break, but Liverpool are at least on course to extend their unbeaten record against Everton to 22 matches.
With strict social distancing measures still in place, the Reds were forced to get changed for their latest clash in the car park at Goodison, with a large portacabin erected just outside the ground.
The tunnel inside Everton's famous stadium has been deemed too small to allow safe and hygienic entry for players, which means all teams visiting over the next few weeks will have to take the same route onto the pitch.
Following Wednesday's match against Palace, Klopp's men will then benefit from an eight-day break before coming up against City at Etihad Stadium on July 2, which could potentially be a title decider.