Javi Gracia believes Watford can spoil Ole Gunnar Solskjaer's debut as permanent Manchester United boss.
Solskjaer's successful spell as interim manager has earned him a three-year contract and Saturday's Old Trafford appointment with the Hornets will be his first outing since the news was announced.
Watford have lost their last eight games against the 'big six' but Gracia insists recent results proves his players should not be overawed.
"I'm sure that to play against Manchester is always very difficult and very demanding," Gracia said.
"They have a very good squad and can achieve whatever they want. They are continuing in the Champions League and are playing in the Premier League.
"But we've also always competed really well against them. Losing the games, but they've always been very close games – 1-0, 2-1. I'm sure we'll have our opportunities if we play as I know we can."
United are hoping to avoid a third straight defeat, but Gracia insists they have all the ingredients needed to be successful.
"First of all, congratulations to Ole. In this moment United are one of the teams in better form. They are playing really well," Gracia said.
"If the club extends his contract and the manager decides to stay, it's because all of them are happy there.
"They are in a good position to improve and grow. They have good players and all they need. They can achieve whatever they want."
