The Brentford forward Clayton Donaldson claims to have witnessed on-field tensions between Chelsea players during the sides' FA Cup fourth-round 2-2 draw on Sunday and is convinced the League One team can exploit the tinderbox atmosphere at Stamford Bridge and embarrass the European champions in their replay next month.

Donaldson, Brentford's top scorer with 19 goals, claimed to have heard Ashley Cole regularly bemoan the lack of movement of Chelsea's front-line, which was spearheaded initially by Fernando Torres, at Griffin Park. Donaldson was asked to play a selfless role on the right of a five-man midfield, a tactic geared specifically towards snuffing out Cole's threat down the left, and it took an equaliser from Torres seven minutes from time to secure the Premier League side a rematch.

Asked if he had witnessed Chelsea's players becoming agitated on the pitch, Donaldson said: "Absolutely. I was obviously closer to Ashley. He was always mumbling something, always mumbling stuff quietly, but I could still hear what he was saying. He was just getting frustrated. He was saying about the forward players not showing, saying things like 'He needs to be there' and pointing. You could just see straight away that he was getting frustrated. That was a good thing.

"We are confident. That [atmosphere at Stamford Bridge] has played a part in their recent form. Obviously the fans are unhappy with the manager – they don't really like him – so any little thing that goes wrong, they're always on their backs. I think that has played a part in their recent results so, hopefully, we can put that to our advantage and the take the positives and unrest their fans again at their place."

The two games against the Premier League club could end up earning Brentford around £1m, a vital injection of funds at a club that recently revealed it had recorded a loss of £5m for 2012. They retain aspirations to reach the Championship, with players likely to arrive on loan in the window between 8 February and 24 March to bolster that promotion push. Certainly, if nothing else, confidence has been pepped against a team who have lost only once in the FA Cup in normal time since 2006.

Donaldson added: "You couldn't really see that they were European champions. We set out to unsettle them, and we did that. They didn't really create that many chances, which I am very surprised about to be honest, especially with the quality of players they have got. That was down to our hard work. We'd done our homework on them and we stopped them creating. We have to take some credit for that. We're confident, especially given their run of form at home recently not having been the best. The pressure will be on them again."

Chelsea will deliver their written submission on Tuesday as they seek to fight the Football Association's attempts to extend Eden Hazard's three-match ban for his ill-judged attempt to kick the ball out from beneath a time-wasting ball-boy at Swansea last Wednesday. An independent regulatory commission is due to hear the case later this week.

The Premier League club will cite video evidence which appears to show Hazard making contact solely with the ball. They will also point to an incident involving Swindon's Matt Ritchie in a League Two fixture with Oxford a year ago when the visitors' winger clashed with a 16-year-old ballboy at the Kassam stadium. Ritchie was booked at the time and subsequently apologised, with the FA opting against taking further action.