Arsenal's already tricky third round FA Cup replay at home to Swansea on Wednesday has been made tougher still given they are set to be without both Mikel Arteta and Laurent Koscielny.
Midfield playmaker Arteta missed Sunday's 2-0 home Premier League defeat against champions Manchester City with a calf strain suffered in training earlier in the week and manager Arsene Wenger does not expect to have the 30-year-old Spaniard back for three weeks at least.
"It is a blow because in midfield he gives us experience, stability and tactical knowledge," said Wenger. "We will miss that."
Arsenal have not won a major trophy since they last lifted the FA Cup in 2005 and their task was not made any easier when Koscielny was sent off just 10 minutes into Sunday's match for a foul on Edin Dzeko.
Now the banned central defender's place is set to be taken by German international Per Mertesacker.
The Gunners are having to replay against a Swansea side held to a goalless draw by Everton on Sunday after a thrilling encounter at the Liberty Stadium ended all square at 2-2.
Two goals inside the final 10 minutes from Lukas Podolski and Kieran Gibbs appeared to have turned the tie Arsenal's way after in-form Spanish striker Michu had given the Swans the lead, but there was still time for Danny Graham to rescue a replay for the Welsh club.
The winners of Wednesday's match will be away to second-tier Brighton, FA Cup finalists back in 1983, in the fourth round.
Another all Premier League third round replay on Wednesday sees 11-times record FA Cup winners Manchester United face West Ham, the last of whose three FA Cup triumphs came as a club in the old Second Division in 1980.
Premier League leaders United head into the match at Old Trafford buoyed by a 2-1 win at home to old rivals Liverpool whereas the Hammers suffered a 3-0 league loss at Sunderland.
Asked if West Ham could recover quickly, manager Sam Allardyce said: "I hope so, we have always managed to bounce back before."
Only an injury-time goal from in-form striker Robin van Persie saw United to a replay in a 2-2 draw in the original tie at Upton Park.
And for all United's success on other fronts, manager Alex Ferguson would dearly love to end the club's nine-year wait for FA Cup glory.
"We want to stay in it and have a go at it this year," he said ahead of a replay that will see the winners into a fourth round clash with either top-flight Fulham or Championship side Blackpool, who meet again on Tuesday.
"We have had some terrible draws over the years and been knocked out early and we don't enjoy that," Ferguson added.
The pick of Tuesday's ties sees an all Premier League clash between West Bromwich Albion and basement club Queens Park Rangers.
FA Cup 3rd rd replays (1945GMT unless stated)
Tuesday: Birmingham v Leeds, Blackpool v Fulham (2000GMT), Bournemouth v Wigan, Brentford v Southend, Leyton Orient v Hull, MK Dons v Sheffield Wednesday, Stoke v Crystal Palace, Sunderland v Bolton, West Brom v QPR (2000 GMT)
Wednesday: Arsenal v Swansea (1930GMT), Manchester United v West Ham (2005GMT)