DI MATTEO: LAMPARD OUT, MARIN AVAILABLE
The midfielder was substituted early on in our defeat to Shakhtar, and Di Matteo admits Lampard's is likely to be absent for two to three weeks, though we are boosted by the return of Marko Marin following injury for what is shaping up to be a tantalising Barclays Premier League fixture.
Di Matteo also answered questions on the nature of our Champions League defeat and the continuing debate of racism in football.
On Sunday's game
Lampard's injury is the only new problem for Di Matteo to deal with, though John Terry serves the second match of his four-game suspension.
'Frank is going to be out for a few weeks. He's got a calf problem, so we will miss him and it's a big loss for us,' Di Matteo said. 'Apart from him everybody else is fit. Marko Marin might be in the squad for Sunday.'
We approach the game four points clear of United at the top of the table, but the manager insists the game comes too early in the campaign to have any major impact on the title race.
'It's still a little bit early in the season for a game like this to be decisive. They are a great competitor of us, we are playing at home and we want to keep our home record very good, have a good game and keep the distance from them. It's a massive game for both clubs, a classic in the fixture list.
'We are still in good shape I think and this group of players always responds to a bad result.
'We always pay attention to players' behaviour and the mood in the camp, so certainly after defeat it is not the best within the dressing room but we have a great game coming up and we can show everybody we are a strong team.'
United's defence has been a cause for concern recently, with only one clean sheet in their last seven games, combined with mounting injuries, taking their toll.
'They are conceding a few goals and we have a big threat as well and we will try to explore those weaknesses,' said Di Matteo. 'We know Man United very well and it's going to be a tough game. They are always very difficult games and we have to take advantage of playing at home and play with the belief and confidence we've been playing with so far.'
Despite their porous defence, United's attack looks as formidable as ever following the addition of Robin van Persie over the summer.
'He's been a very good signing for them and has scored some vital goals already,' the Italian assessed. 'They had a very good start, they recovered from their first defeat in the first game and are a strong team. They were at the top last season and they have added to it, so you wouldn't expect them to be anywhere else.'
On Tuesday night in Donetsk
Di Matteo drew similarities between our defeat to Atletico Madrid in Monaco and Shakhtar in midweek.
'We conceded an early goal in both games and lost our composure a bit. We have to learn from that and stick to our organisation and game plan,' he admitted.
'[Donetsk has] been a long trip, coming back as well. Not much sleep in the night and I think we were all very disappointed with it. If we scored a bit earlier we felt we would have had a good chance to equalise but we have to look forward now and focus on the game on Sunday.
'When you concede an early goal it is always a bad start to a game. Starting the game well is very important in both halves and also being disciplined with organisation and not losing that, even if you do concede an early goal.
'We base our game on being solid first of all and then trying to attack, create chances and score goals. I don't think in all the games it's been like, "You score one we score two". We've been more disciplined than that, but if you concede an early goal you are chasing straight away. We need to pay attention to that but in general we've been organised and the balance has been good as well.'
On Kick It Out and the PFA's Six-Point Plan
Di Matteo said he will not force any of his player's to wear t-shirts supporting the Kick It Out anti-racism campaign, but it would be his preference that they do.
'We are supporting the Kick It Out campaign, it's going to be an individual choice for our players and we're not going to force anybody to or not to wear it,' he said. 'My personal opinion is we should wear it, raise awareness for it and show support for it.
The PFA this week announced plans to deal with racism in the game, which included the introduction of an NFL-style 'Rooney rule', where qualified black coaches are placed on interview lists for job vacancies, and racial abuse would be considered gross misconduct.
'I think if it will become a rule we will play by the rules as we have always done,' said Di Matteo. 'As a club we are against any kind of discrimination and if it goes through we will support it.
'Despite your background if you are qualified and good enough, if the employer thinks you're good enough there shouldn't be such an issue. I know in the States they have this, do we need to come down to a law like that? I am not sure. There should be freedom of choice and everybody should have equal chances.
'If the majority believes we need a law like that, then we will obey it and support it.'
Although Sunday's game is a sell-out, there are still hospitality tickets available for Wednesday night's Capital One Cup clash with United. Visit Chelsea's Hospitality site for details.