Manchester United boss Louis van Gaal was full of praise for Southampton ahead of Monday's game at the St Mary's Stadium.
The Red Devils will leapfrog the Saints with a win but the Dutchman says it will not be an easy task for his players.
"I think they have a very good squad," van Gaal said.
"A lot of players I know. A lot of players were offered to us and I think they are able to come in the first four but that is also because I believe in the management, in Ronald Koeman and his brother [Erwin].
"It is also a surprise that a club like Southampton is in that position but it is always a matter of coach, players and staff."
United welcome striker Wayne Rooney back in the squad but other players will continue to be on the sidelines, including Argentina's Angel di Maria.
"It's not a bad injury, but I am not a doctor," van Gaal said on Di Maria's injury.
"I have to say it like a manager, not like a doctor. But I think he shall recover very quickly.
"[Jonny] Evans is coming back. He is fit to play.
"[Phil] Jones is coming back but not fit to play. He needs training sessions and maybe also matches in the second team. But he is coming back. He is fit to train. That is also very good. We are seeing already light in the tunnel."
