Virgil van Dijk didn't train with Liverpool in the Reds' first session since arriving in Qatar for the Club World Cup.
But there has been no suggestion that the centre-back is suffering with an injury.
Jurgen Klopp led his squad in a session at the Qatar University campus in Doha on Monday, with Gini Wijnaldum also not featuring after he went off with a muscle problem in Saturday's 2-0 Premier League victory over Watford at Anfield.
Wijnaldum's fellow Dutchman Van Dijk played the full 90 minutes in that game, but as reported by the Liverpool Echo there has been no injury reason given for his absence from training as the squad prepared to take on Mexican outfit Monterrey on Wednesday.
It could just be that Klopp has afforded Van Dijk a rest amid a hectic schedule and due to his importance to the squad amid defensive injuries elsewhere.
Van Dijk was joined in defence by Joe Gomez for the victory over Watford, with both Joel Matip and Dejan Lovren out through injury.
Neither Matip nor Lovren are in the squad for Qatar, and the Croatian has offered an update on his injury via his Instagram account.
"Not the best time to be injured, but as u know me I will be back again stronger," he wrote.
"Hard work begins behind the scenes so I can be asap on the pitch.
"In the meantime I wish my teammates and Liverpool all the luck at the club world cup. Boys come back with another trophy."
The Reds face their Liga MX opponents at 5.30pm GMT on Wednesday, with a place in the Saturday final against either Brazilians Flamengo or Saudi side Al-Hilal up for grabs.
