Chelsea looking light on personnel ahead of another visit from the Reds

Robin van Persie evades the challenge of Csar Azpilicueta on Sunday - will United get away from Chelsea again when they meet on Wednesday?

Roberto di Matteo's men face Manchester United again on Wednesday night but could this be the moment when the lack of numbers in the Chelsea squad begins to show? Ralph Ellis suspects that will be the case...

When the luck of the draw forced Chelsea to face Manchester United twice in four days, who would have thought it might be the Capital One Cup tie which would be a defining contest?

Yesterday's dramatic, controversial encounter at Stamford Bridge brought Sir Alex Ferguson's side to within a point of the Blues at the top of the table. It ended with Betfair's market making the decision that United should now be considered 2.829/5 favourites to recapture the Premier League title.

Yet we may actually know more about the relative strengths of the two clubs fighting to knock Manchester City off their perch after Wednesday night. Teams win matches, but squads win titles - and this will be the first proper chance to evaluate what lies underneath the star players at Stamford Bridge.

It's a piece of knowledge that will be especially relevant in the assessment of whether European Champions Chelsea are ready to go the distance in the domestic competition. So far Roberto Di Matteo has hardly rotated his team at all, playing 15 matches while relying essentially on the same 14 players. That cannot last.

The red cards dished out to Fernando Torres and Branislav Ivanovic yesterday were a sharp reminder that suspensions happen. Injuries happen too. And while Aston Villa might have won the old First Division in 1981 using only 14 players, it simply can't be done now. (And certainly not by Villa on the basis of their showing at home to Norwich, but that's another story).

When Chelsea walloped Wolves 6-0 in the last round of the Capital One Cup, it was an opportunity for the Stamford Bridge faithful to have a first look at the likes of Lucas Piazon and Csar Azpilicueta. They liked what they saw. Lucas is an 18-year-old Brazilian who is billed as the next Kaka, while Spaniard Azpilicueta is a 23-year-old dashing, attacking right back.

But whether they can yet be relied upon in big matches will be a different matter. Both were pretty much considered as players for the future, but if Chelsea are to last the pace in the race to finish first in the Premier League, and make a decent defence of their Champions League trophy, they will have to step up to the plate much earlier.

Can they handle big match atmosphere? Can they perform when it really matters? Events yesterday have added a whole deal of spice to Wednesday's cup tie and while winning or losing won't add points, or take them away, from the league table there is considerable extra incentive. Following on from the Champions League defeat away to Shakhtar Donetsk, Chelsea have now lost two in a row. Three would not be good.

Chelsea are 2.3811/8 favourites to win Wednesday's Cup tie, and I'm not sure there's too much value in that. United will no doubt use their squad too, but it already has more proven depth. Sir Alex has rotated his team around 20 main players so far, although he also gave chances in the Old Trafford win over Newcastle in this competition to youngsters.

The difference is that nobody is expecting kids like Scott Wootton or Will Keane to play important roles in the Barclays Premier League later in the campaign.

But in Chelsea's case the lack of numbers in their squad means at some stage they will be forced to convert their up and coming into here and now. Are they ready? We'll know far more by Wednesday night.