Chelsea's record goalscorer was slated to start Wednesday's win over Singha All-Stars in Bangkok, but appeared with strapping and ice on his right ankle due to an Achilles injury.
The Blues tackle a Malaysia XI in Kuala Lumpur on Sunday, but Mourinho is taking a long-term view and is not prepared to take any chances of the 35-year-old exacerbating the problem.
"I don't want to risk," Mourinho said.
"It is such a long pre-season we don't need to risk, especially on these pitches, which are not the best quality pitches. If on Sunday he is not 100 per cent, I am not risking him.
"He is an important player for us."
Lampard surpassed Bobby Tambling as Chelsea's record goalscorer in April before agreeing a one-year contract extension to end a saga which rumbled on for much of last season.