League One MK Dons and Southend United from League Two both have to overcome teams from a division above if they're to win plum ties in Round Four of the FA Cup.
The Dons will travel to either Premier League sides West Bromwich Albion or Queens Park Rangers if they beat Sheffield Wednesday at Stadium MK. Victory for Southend over Brentford will land them a home clash with mighty Chelsea.
No doubt that Roots Hall will be rocking if they get the honour to host the European champions again, just as it was four years ago for a Third Round replay.
Back in January 2009 Southend - under manager Steve Tilson - held Chelsea to a 1-1 draw at Stamford Bridge, only to lose the replay 4-1 on home soil after taking the lead through Adam Barrett.
But the Shrimpers, now with Paul Sturrock in charge, will have to turn the form book upside down at Griffin Park. They've gone five games without a win, including a draw with Brentford in the original tie.
Brentford have lost just one of their last twenty games, that defeat ironically against Southend in the Johnstone's Paints Trophy.
MK Dons used their undersoil heating system at Stadium MK for the first time ahead of the meeting with Championship strugglers Wednesday, to beat the winter weather.
The original Third Round tie at Hillsborough ended in a goalless draw, but the Dons are seeking their first ever victory against the South Yorkshire club.
You can get minute-by-minute updates on both ties by clicking on the teams below:
FA CUP RD ROUND REPLAYS
Brentford v Southend United
MK Dons v Sheffield Wednesday