Erik ten Hag's sacking has added chaos to Chelsea's week, with Enzo Maresca's analysts having already conducted extensive homework on how Manchester United played under the Dutchman.
Chelsea travel to Old Trafford next in the Premier League and now, Maresca has had to begin watching PSV games from when they were managed by Ruud van Nistelrooy in preparation.
The analytical team may even have to switch to studying Ruben Amorim's Sporting Lisbon if the Portuguese is appointed in time to take charge of Sunday's showdown.
Speaking ahead of travelling to Newcastle for Wednesday night's Carabao Cup clash, Maresca said: 'I guess it would be Ruud [in charge of United on Sunday]. He's a friend of mine. We played together [for Malaga in 2011-12]. We still have relations.
'We have started to watch some PSV games. Unfortunately, we had already watched many Man United games. At the moment, I'm sad for Erik. But at the same time, I'm happy for Ruud. Hopefully, I can see him on Sunday.'
Chelsea manager Enzo Maresca will take his side to Manchester United on Sunday afternoon
Maresca watched last season's Carabao Cup final which Liverpool won 1-0 by beating Chelsea, but he said he did not notice the infamous 'billion-pound bottle jobs' comment from Gary Neville on co-comms.
'The only thing I can say is that I still remember from when I was watching television, they showed the difference, the amount of finals that Liverpool and Chelsea players had played,' Maresca said. 'The difference was huge.
'The reason I have said that probably in this moment we are not close is because you need to live moments. You need that experience.'
Meanwhile, Chelsea have been contacted by Thomas Tuchel's England for their goalkeeping coach Hilario.
Currently, however, the former Blues shot-stopper is still working for the Premier League club.
Chelsea's second-choice goalkeeper Filip Jorgensen will get his chance to impress against Newcastle on Wednesday with pressure on Robert Sanchez to keep his place as No 1.