Saturday 28 May at 16:31 : May 28 (GMM) The participation of three drivers is in doubt for Sunday's Monaco grand prix.

The two HRT drivers, Vitantonio Liuzzi and Narain Karthikeyan, have failed to qualify. Liuzzi crashed on Saturday morning and his F111 was not repaired for qualifying some hours later.

Indian Karthikeyan, meanwhile, also failed to set a time in Q1 with a reportedly unrelated suspension problem. Neither driver has looked competitive all weekend and are therefore unlikely to receive dispensation by the stewards to race.

Sergio Perez, meanwhile, is in hospital on Saturday afternoon nursing a sore head and leg.

The Mexican crashed heavily on the exit of the tunnel despite qualifying for the 'Q3' segment in Monaco.

He speared at high speed into the divider between the track and the run-off zone; an area narrowly avoided in the morning by Nico Rosberg, who had a near-identical crash.

Perez appeared unconscious immediately after the crash but was reportedly talking to medics as he was loaded into the ambulance.

Sources report he is complaining of leg and head pain. "I'm not sure he will be racing tomorrow," said Jenson Button, who was injured in a similar crash in 2003.

Karl Wendlinger suffered serious head injuries in the same place in 1994.

"That's an area we have to have a look at. There's a few places around here like that," agreed Mark Webber, third on the grid behind Button and pole sitter Sebastian Vettel.

Said Team Lotus executive Riad Asmat: "The early news is that he (Perez) has taken a knock but is ok so that's encouraging."

Agreed Red Bull's Christian Horner to German Sky television: "The initial information is positive. We have heard he is reacting to the doctors."