Salah, 33, was substituted in the 59th minute at Anfield after going down clutching his left leg.
The Egyptian international announced last month he will leave Liverpool at the end of the season, giving him a month to recover before the Reds' final game of the campaign against Brentford at Anfield on 24 May.
"It's too early to say but we all know Mo and how hard it is for him to leave the pitch," Slot told Match of the Day.
"For Mo to leave the pitch, it shows you something but we have to wait and see how bad it is."
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Liverpool not a team that 'pretends' to be injured - Slot
Salah was able to walk from the field unaided but took his time as he did so and turned to applaud all sides of Anfield.
Salah joined Liverpool in 2017 and has won two Premier League titles, the Champions League, Fifa Club World Cup, Uefa Super Cup, FA Cup and two EFL Cups, as well as the Community Shield, in an iconic career.
His tally of 257 goals in 435 appearances for the Reds has him third on the club's goalscorers list, behind Ian Rush (346) and Roger Hunt (285).
Slot said he believed the fact it could be the Egyptian's final game for the club will have been on his mind as he was substituted.
"My honest answer is yes, the way he came off," Slot told Sky Sports.
"It went through his mind because there are only a few weeks to go but we are hoping he plays for us again.
"You have tests to do and then we have to wait for the prognosis."
Any issue would likely rule Salah out of a final Liverpool appearance away against rivals Manchester United next Sunday. He has scored 16 goals in 18 Liverpool appearances against United.
After that, Liverpool host Chelsea on 9 May and travel to Aston Villa on 17 May before their season concludes against Brentford.
