A header from Mark Hughes challenged the logic of Arsenal's earlier superiority at Highbury last night and offered Chelsea renewed hope for their return leg at Stamford Bridge.

That had begun to appear a formality after Marc Overmars's fifth goal in as many games had given Arsenal the lead midway through the first half and Stephen Hughes's first of the season extended it in the opening minute of the second. Then his namesake came off the Chelsea bench for the last half-hour and within nine minutes had scored from Gianfranco Zola's cross.

Until the quarter-finals neither team gave the impression that winning this trophy had crossed their minds. Before winning at West Ham Arsene Wenger had sent out sides heavily sprinkled with reserves and Ruud Gullit's team rotations embraced Stamford Bridge teenagers until Chelsea beat Ipswich in a penalty shoot-out.

Last night any such decisions were taken out of both managers' hands by international calls and injuries.

Yet the in-form Dutch partnership of Dennis Bergkamp and Overmars was intact and Arsenal's main hope of a significant lead for the return leg lay with them. Gullit's team selection also left Highbury feeling optimistic.

The Chelsea manager played himself but not for the first time left Hughes and Gianluca Vialli on the bench. Zola and Tor Andre Flo wasted little time getting among the Arsenal defenders but the absence of Dennis Wise and Roberto Di Matteo from Chelsea's midfield more than offset the opposition's loss of Patrick Vieira.

Flo's was the first scoring attempt, a shot deflected behind off Tony Adams, but largely it was a matter of Chelsea trying to clog up their half with bodies in the hope that Arsenal's lines of communication with Bergkamp would be disrupted.

No real contact was made for 15 minutes, then Bergkamp all but scored. Stephen Hughes's pass found Nigel Winterburn in space on the left and the full-back's centre saw Bergkamp leap between Gullit and Steve Clarke to beat Ed De Goey with a header that struck the bar.

Midway through the first half Arsenal duly took the lead. Three Dutchmen were involved in the goal but Bergkamp was not one of them.

It was a simple affair. Emmanuel Petit's forward lob caught Chelsea pushing up with Overmars running past them but on-side. Gullit tried to intercept the ball but back-headed it into the path of Overmars who slipped a low shot past De Goey.

Zola almost organised an immediate response by finding Flo with a short square pass through a thicket of defenders, but Flo's touch let him down enabling Alex Manninger to gather the ball.

Five successive corners for Arsenal found Chelsea trapped in their goal-mouth. Gullit, generally off the pace of the game, looked badly short of match practice. After half-time he moved himself from defence to midfield and replaced a Romanian, Dan Petrescu, with a Frenchman, Laurent Chalvert. But it made little difference.

In the first minute of the second half Arsenal scored again. After Bernard Lambourde lost the ball in midfield, Hughes began a move which saw Overmars exchange passes with Nicolas Anelka before reaching the left-hand byline. The Dutchman laid the ball back and Hughes thumped it home.

The uncertain state of Chelsea's defence, allied to Arsenal's attacking appetite, suggested the scoring would not end there. Gullit replaced Flo with Hughes on the hour but at that point it looked a forlorn gesture.

But not quite. In the 68th minute a marvellous save by De Goey, diving full length to keep out Bergkamp, denied Arsenal a third and the next minute Hughes headed Chelsea back into the contest from Zola's cleverly-flighted cross.