Vieira's hamstring injury, sustained early on in Saturday's Premiership match at Wimbledon, will keep him out for at least three weeks. Now Petit, suspended tonight, could be missing for the same period with an abdominal problem picked up at Selhurst Park, and so might Bergkamp, who came off with a tight calf.
It is the third successive Champions' League game in which Arsene Wenger's side will be badly under-strength. The French midfielders were absent at home to Dynamo Kiev, when Arsenal drew 1-1. They returned for the 3- 1 defeat in the Ukraine when Bergkamp, Nicolas Anelka, Marc Overmars and Tony Adams were missing. That night Arsenal fell from top to bottom of a group in which the four teams are separated by a single point.
The section could be turned on its head again tonight. Victory over Lens and a draw in the other tie, between Kiev and Panathinaikos, would put Arsenal on top again. They would then need to win in Athens to be sure of qualifying.
Their personnel problems also have serious implications for Arsenal's defence of the Premiership title, but yesterday Wenger would not discuss that. Of the Nigerian striker Nwanko Kanu, a possible recruit on loan from Internazionale, Wenger said: "He is one of 10 players offered to us every day." After almost six hours without a goal, some think Wenger should grab a couple of them.
He prefers to play the long game, putting responsibility on the shoulders of the 19-year-old Anelka. It would make sense to play Christopher Wreh alongside him tonight, while Overmars overran Lens in France after half- time, scoring and hitting the post and bar. They might be tempted to fill the hole in midfield by pushing Martin Keown forward and bringing in Steve Bould at the back.
Wenger added: "We play in a collective sport. We can compensate for losing an important player. If everyone gives one per cent more, it's an extra 11 per cent."
Lens' French league form has been so modest - seven defeats in 15 games - and their coach, Daniel Leclercq, recently offered his resignation, which was not accepted. They will be seen literally, in their true colours, which are not red and yellow, but Sang Et Or (blood and gold). Blood and guts may be necessary as this group moves towards a climax.
Arsenal (possible): Seaman; Dixon, Bould, Adams, Winterburn; Vivas, Parlour, Keown, Overmars; Anelka, Wreh.Reuse content