It was originally feared Lampard was facing a six-week lay off after damaging his thigh while on England duty.
The midfielder spent seven hours cramped on a plane on the way to Qatar for Saturday's Brazil friendly.
Lampard strained his left thigh while sprinting during England's first training session.
But Chelsea have confirmed the midfielder will be out for three weeks with a muscle tear.
A Chelsea spokesman said: "It has been confirmed that Frank suffered a muscle tear in his left thigh while away with the England national team.
"The midfielder reported back at Cobham this morning (Friday), having flown back from the Middle East.
"The Chelsea medical department's initial impression is that he may take approximately three weeks to recover."
Chelsea will claim his £151,000-a-week wages in compensation from the Football Association while he is sidelined.