Lampard was again an unused substitute this weekend in Chelsea's 4-1 win over Swansea.
The England international has started just once in four games for the Blues and was substituted at half-time.
The 33-year-old left the bench early on Saturday after youngster Josh McEachran entered the game in place of Raul Meireles.
Speaking after the match, manager Andre Villas-Boas insisted that Lampard remains a part of the team.
"I don't know but this is nothing to speculate about," the Blues boss is quoted as saying in the Daily Mail. "They are team players and the players want the team to perform, and Frank is like that. He is a fantastic player, a magnificent player and soon he will be back to the team, sooner than you expect.
"The decisions today were mainly based on the fact we played 120 minutes [in the Carling Cup] on Wednesday and these players were fresh, apart from John Terry and Petr Cech. In a tight calendar like we have, it's important to have squad rotation."
A start or substitute role this weekend would have marked the midfielder's 350th league appearance for the club, who he joined from West Ham United in 2001.