The 29-year-old Czech Republic international, who now plays in protective headgear after fracturing his skull in a collision with Stephen Hunt of Reading five years ago, was forced off at half-time after a collision with Fulham debutant Orlando Sa.
Chelsea were already without injured No.2 Hilario, meaning losing Cech left them with third-choice Ross Turnbull as their only other recognised first-team goalkeeper.
Turnbull had to face a penalty just after coming on but his goal survived intact as Fulham's Pajtim Kasami fired his spot-kick against the bar.
However after their 4-3 penalty shootout win Following a 0-0 draw, Villas-Boas said Cech had been given the all-clear.
"Petr went for a scan in the hospital and he's OK," he told reporters.
"He felt a little bit dizzy from the early concussion at half-time. We decided, and he decided as well, it was better not to take risks."
Cech should be fit to face Swansea City at Stamford Bridge on Saturday.
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