Gus Poyet is convinced Jose Mourinho's return has made Chelsea genuine Barclays Premier League title contenders once again.
The former Blues midfielder will lead the Black Cats into battle with Mourinho's men at the Stadium of Light on Wednesday evening desperately looking for a fourth successive home victory in all competitions to help ease their relegation fears.
However, while that might prove a blow to the second-placed London club's hopes of reeling in leaders Arsenal - the Gunners are currently four points better off - the 46-year-old is confident they will be involved in the mix come the end of the season.
Asked if Chelsea, who came from behind to beat Southampton 3-1 on Sunday, could go all the way as a result of Mourinho's return to Stamford Bridge, Poyet replied: "Yes, no doubt about it.
''They are different, they are stronger. The reaction at the weekend at half-time was all about the mentality of the team more than even the play or the technique or the ability.
''It was mental. It was a completely different team in the second half. I am sure there was a unique half-time team-talk in the dressing room or wherever it happened. It was a complete turn-around.
"I know him (Mourinho) and I admire him a lot. He's a different-class person and manager. I know him in football ways and as a person and I am looking forward to seeing him before the game.
''Then the game is the game and I hope everything goes all right and there are not any problems in the game between the benches.
''I had the opportunity to watch him training a few times at Chelsea and it was very impressive.''
Sunderland, of course, are currently scrapping at the opposite end of the table, where they remain five points from safety despite a significant upturn in results since the Uruguayan's arrival in October.
Newcastle and Manchester City have both left Wearside pointless with the Saints also bowing out of the Capital One Cup, and while an extension of that run may sound a tall order, that is exactly what Poyet is targeting.
He said: ''We know they are one of the best teams in the country and that we need to be very, very good.
''We are going to have to compete, defend well. I don't know how many chances we are going to create because they are one of the teams which defends the best in England, so there are plenty of things we need to be good at.
''But we all believe it is possible, especially after beating Manchester City at home. That shows you there is a way and hopefully we can repeat something like that.''
And Mourinho believes Sunderland should be higher up the table.
''I was analysing their match against Newcastle at home and Man City at home, these were the matches I focused on,'' the Portuguese said.
''I think they are better than the points they have, the quality of their players is not comparable with some teams in that part of the table but I think they are in a moment where one point doesn't make a big difference.
''They need three points, they need two or three victories to get out of the dangerous area. I don't think they can play in a defensive way, that is why they have a positive approach because they need to win matches.
''I think Gustavo's style is to try and play good football, I think we have two very difficult matches.''
Mourinho confirmed striker Samuel Eto'o could feature at Sunderland following a groin injury but the Blues will be without David Luiz and Oscar.
The Portuguese also expects Ashley Cole to start one of the next two games after the England international lost his left-back berth to Cesar Azpilicueta.