The 21-year-old was almost four-and-a-half seconds slower than leader Rubens Barrichello and had to embarrassingly circuit the track on three wheels after his right rear wheel fell off.

Monaco-based Button eventually wound-up in 21st spot with only Tarso Marques behind him, with the Brazilian seeing his second session curtailed by a blown engine in his European Minardi.

The Frome-born racer was behind 19-year-old Spanish rookie Fernando Alonso, who was 17th in the other Minardi despite only stepping into the car last week and having done no testing.

Italy's Giancarlo Fisichella completed a miserable day for Benetton by finishing in 16th place.

Button, on a two-year loan deal with Benetton from Williams, with whom he finished eighth in his maiden season last year, has admitted that the team were behind schedule in developing the car.

But he would still have been looking for a better performance and now faces a repeat of last year's dismal qualifying session when he also finished 21st.

The performance of the Ferrari duo - before Schumacher's accident - was an ominous warning shot to their McLaren rivals David Coulthard and two-time former champion Mika Hakkinen.

Coulthard was fourth fastest, 0.35 secs adrift of Barrichello, with Hakkinen one place further back but nearly another half-a-second adrift.

Eddie Irvine was 13th fastest for Jaguar Racing, whose new driver Luciano Burti, in only his second race, caused the first red flag of the season to stop the session after sliding backwards into a wall.

Finland's Kimi Raikkonen began to answer the critics who claimed he should not have got an F1 seat after just 23 car races with a creditable 11th place for Sauber.

Colombia's Juan Pablo Montoya, who replaced Button at Williams, was 15th while the other debutant, Brazil's Enrique Bernoldi, was 20th for Arrows.