Blackburn's odds will have shortened with the news that Newcastle will probably be without Paul Bracewell and Peter Beardsley through injury, and Philippe Albert and Scott Sellars are still long-term casualties.
Kevin Keegan, the Newcastle manager, is refusing to gamble on the influential Beardsley's fitness, and admitted: "Peter is struggling and we won't risk him unless he's 100 per cent. People portray the Blackburn tie as do or die, but there is an awful lotof football left to be played, and we won't risk putting Peter out for a long time."
Chris Sutton's 18th goal of the season gave Kenny Dalglish's men the half-time lead they deserved in the first game, but a superb strike from Robert Lee rightly earned Newcastle their second chance.
"We more than matched Blackburn in the first game," said Barry Venison, who did not play down the threat posed by Blackburn. "They're the best team in the country at the minute and we know they will be difficult to break down.
"We've lost Andy Cole - of course that's a blow and it's been talked about a lot since he moved last week - yet we showed against United that the players we've still got are well capable of beating anybody, and that includes Blackburn."
Newcastle's new signing, Keith Gillespie, will be on the sidelines as he is ineligible until the fourth round, so Keegan will probably name the side on duty on Sunday. Blackburn are also likely to stick with the team which beat Nottingham Forest 3-0 at the weekend.
Tim Sherwood, the Blackburn captain, completes a two-match ban, so Paul Warhurst will continue in midfield, while the ankle injuries which ruled Graeme Le Saux and Stuart Ripley out of Saturday's game mean another chance for Alan Wright and Robbie Slater.
John Barnes faces a fight to reach fitness in time for Liverpool's third-round replay with Birmingham at Anfield tonight. He missed Saturday's Premiership defeat against Ipswich because of a thigh strain, and Michael Thomas will again deputise if the England midfielder misses out.
The Arsenal centre-half, Steve Bould, faces a late fitness test to see if he can return to the defence for tonight's replay against Millwall at Highbury.
Bould missed the 1-1 draw against Everton on Saturday with a groin injury, and with Tony Adams still recovering from an Achilles operation, George Graham, the Arsenal manager, badly needs Bould's authority and experience.
If fit, he will replace either Martin Keown or Andy Linighan, but Arsenal have other problems with Stefan Schwarz and Paul Dickov suspended, and their new signings, John Hartson and Chris Kiwomya, cup-tied. Kevin Campbell is recalled to partner Ian Wright in attack.
Following his yellow card on Saturday, Wright is now one booking away from the 41-point mark, which would mean a visit to the FA and almost certainly his third suspension of the season.
Given the reception Wright received from the Millwall fans at the New Den in the first match, before which he accused some of their fans of racist behaviour, he will be under pressure to keep his temper in check, as will the fans. Police at Highbury havebeen put on alert to prevent a repeat of the trouble which followed the game at Millwall, when 90 arrests were made outside the ground.
Millwall may be forced to plunge their Australian trialist, Alistair Edwards, into the match at Highbury. Mick McCarthy, the Millwall manager, brought in Edwards alongside Dave Mitchell at Sheffield United last Saturday because of injuries to Richard Cadette, Greg Berry and Clive Allen.
They are unlikely to be fit for tonight's game, but Tony Witter returns to the defence after suspension. The winners will earn a home tie with Chelsea.