Liverpool boss Rafael Benitez believes Steven Gerrard's recent England outings have taken a toll on the midfielder.
Gerrard was doubtful for England with a broken toe but played in both Euro 2008 qualifying wins over Israel and Russia.
"It could be that playing twice for England has had an impact," Benitez told the Liverpool Echo.
"England knew what I felt about him playing in both games, but everyone was talking about how important this situation was for England."
Gerrard came off with cramp after 71 minutes in the win over Israel before playing the full game when Russia lost at Wembley in two crucial games in England's Euro 2008 qualifying campaign.
But, since his return from international duty, Gerrard has seemed to be struggling to reach his usual all-action style as Liverpool's form has also stuttered.
"His national team is England but it is clear that these players cannot play every game for 90 minutes," added Benitez.
"Gerrard was not 100% physically fresh, I don't mean fit but fresh.
"In these kind of games you need to keep the tempo really high and if you play too many games in a row for 90 minutes, especially if you are not fit then normally you have problems."