Oscar could make his Chelsea debut at Wigan this weekend, but Marko Marin remains out with a hamstring injury.

Our Barclays Premier League kick-off is delayed by a day due to live TV coverage, which has given Roberto Di Matteo extra time to work with his squad, which now includes Oscar, the Brazilian midfielder who is now at Cobham following Olympic duty.

'We only have Marin out injured, everybody else is okay. In terms of the new signings, Oscar has finally joined us after his Olympic Games and they are all available for Sunday,' the manager reported.

'Oscar has only been in the building for a day and a half, so we will see. I still have to think about it for Sunday, but there will be plenty of time to play.'

That may be at the expense of Juan Mata, who it is admitted will need a break from action at some point after a busy summer of football.

'He has had a long summer but I will factor in a break for him at some point because it's important,' conceded Di Matteo. 'He won't be able to go through the whole year like this. We will have to plan it intelligently.'

Sunday though, cannot come quickly enough for Di Matteo, who is looking forward to getting down to business after a challenging pre-season.

'I think it's about time that we started now. Pre-season is always a long period and you look forward to the first game of the season,' he said. 'Pre-season has been a little disrupted by the European championship and Olympic games with players coming back at different stages, so we haven't had that much time to work with the whole team and it will take a bit of time.

'All the players are looking forward to finally starting. Our aspiration is to do better than last season in the Premier League.

'Expectation levels are always high. It might have added a little pressure but it was always so high anyway. It's an ambitious club and we know we have to try and win trophies and be successful.'

As in previous seasons, Di Matteo expects the title challenge to come from four teams.

'I still believe Man City is the favourite. They haven't lost any key players, but Van Persie is a good signing for united.

'We have to try and catch up with the Manchester teams. The gap last season was big so our aim is to catch them up.'

The challenge begins at the DW Stadium on Sunday lunchtime, and Di Matteo recognises a potential banana skin in Roberto Martinez's side.

'It's definitely a difficult fixture,' he said. 'Last season at the end they were very strong. The last 12 games they were very good, we played them at home and it was a difficult game for us. We expect a difficult game on Sunday, they're at home as well so it won't be easy for sure.'

Oscar aside, there will be no new faces in the squad for that game, though further recruits could yet be found before the transfer window closes. Di Matteo insisted though that excessive fees will not be paid.

'We are not going to pay over the top, only what we think is the real value of a player. There won't be anybody coming in for Sunday but apart from that we will keep our transfer policy private.'

One player who has departed on loan, Romelu Lukaku, has been challenged to produce his best form in the Premier League while with West Brom, to give himself the best chance of breaking into the Chelsea team next season.

'I think Romelu has to look forward to his new challenge with West Brom and try to play and score goals, to show his potential. That's what he has to focus on, he had a difficult season last season with not many minutes on the pitch but it's better to look forward than back.

'You can't change what happened in the past but he can certainly influence the picture for himself. We are looking to follow him intensely and see how he does.'