Bradford City will be looking to pull off one of the biggest shocks of this season's FA Cup when they travel to Stamford Bridge to take on Chelsea this weekend.
The League One side, who knocked out a string of higher-ranked teams on their way to the League Cup final a couple of years ago, needed a replay to oust Millwall of the Championship in the third round.
Phil Parkinson's side thrashed 10-man Millwall in their replay last week to set up their clash with the Premier League leaders.
They have been in strong form in the league, with seven wins in their last nine, although they head into this match following a 1-0 defeat to Yeovil Town at the weekend.
Striker Billy Clarke will need a late fitness test to assess whether he is able to feature as he continues to recover from a knee injury, while Andrew Davies is also a doubt after picking up a knock against Yeovil.
Matthew Dolan is expected to travel though, after making his return from a hamstring injury last week, while Jordan Pickford is cup-tied, which should see Ben Williams start in goal.
Meanwhile, Jose Mourinho's side head into this match just a few days after facing Liverpool in a League Cup semi-final, with a second leg and a Premier League tie against Manchester City to come next week.
With that in mind, the manager is expected to rotate his squad for this fixture, having also done so in their win over Watford in the last round.
The likes of Loic Remy, Didier Drogba and Andre Schurrle could all feature to allow regulars like Diego Costa, Eden Hazard and Oscar to rest.
Petr Cech is likely to continue in goal, having been picked in the third round, and with Thibaut Courtois having been dealing with a recent injury.
Chelsea made it to the fifth round last season, where they were beaten by Manuel Pellegrini's side, but they have not lost to lower league opposition in this competition since being beaten by Barnsley in 2008.
This will be the first meeting between these two sides since 2000, when Chelsea claimed a 3-0 win at Stamford Bridge.
Chelsea:
Form in FA Cup: WLWWLW
Form in all competitions: DLWWWD
Possible starting lineup: Cech, Zouma, Luis, Cahill, Azpilicueta, Mikel, Ramires, Oscar, Schurrle, Drogba, Remy
Bradford City:
Form in FA Cup: LLWWDW
Form in all competitions: WWDLWL
Possible starting lineup: Williams, Darby, McArdle, Davies, Meredith, Morais, Dolan, Halliday, Knott, Hanson, Stead
Sports Mole says: 3-0