Claude Puel has questioned Jose Mourinho's ability to make Manchester United's stable of stars work together as Southampton prepare for Friday night's game at Old Trafford.
Southampton were held to a 1-1 draw by Watford on opening day, while United cruised to a 3-1 victory over Bournemouth.
Friday's game will present Puel with a chance to snatch his first Premier League win, a task that could be made even more difficult, with Mourinho expected to hand the world's most expensive player Paul Pogba his debut.
"Pogba has qualities and is a different player who can make a difference in an offensive game and also defensive," Puel said.
"He is always dangerous on the run, but I don't know how his manager can make all these great players work together.
"It is difficult to remain a collective and to have two or three players for every position on the pitch. I'm sure they can be one of the favourites to win the championship. But I hope we can slow them down and take one or all three points from Manchester United.
"The most important thing for us is not to consider them as a great team with great players but to consider them as opponents with good opportunities to make a good game and to make a good result."
Mourinho has a lot of midfield options with Juan Mata, Marouane Fellaini, Morgan Schneiderlin, Ander Herrera, Henrikh Mkhitaryan and Michael Carrick all vying for a spot alongside Pogba. Anthony Martial, Wayne Rooney and Zlatan Ibrahimovic will be the likely trident to lead United's attack.