Lionel Messi started on the bench for Barcelona's La Liga game against Real Betis on Saturday, the first time the Argentinian has been rested by new coach Ronald Koeman.
Koeman's assistant Alfred Schreuder said before the match: "We're not talking about an injury, he's just not fresh.
"He has played a lot of games. Koeman has said if you're not 100 percent fresh, it's better you start on the bench."
Messi has made a slow start to the season by his own high standards. He is yet to score a goal from open play this term, although the 33-year-old has converted four penalties.
Koeman had indicated he would need to rest his captain at some point, especially given Barca's last six games came in 19 days, and Messi started all of them.
The dip in form comes after Messi's failed attempt to leave Barcelona last summer.
Koeman's side sit 12th in La Liga after a disappointing few weeks in the league but have won all three of their group games in the Champions League.