Manchester - Manchester United manager Jose Mourinho wants his side to take the game to Young Boys straight from kick-off when they face the Swiss club in a Champions League tie at Old Trafford on Tuesday.
Victory for Mourinho's men, allied to a Valencia failure to beat Juventus, would see United qualify for the last 16 of European club football's elite competition with a game to spare.
Mourinho slammed United after their lacklustre goalless draw with Premier League strugglers Crystal Palace last weekend, accusing his players of lacking "heart" after they were booed off the field by their own fans at Old Trafford following a result that left them seventh in the table - well adrift of the qualifying positions for next season's Champions League.
He warned then that a repeat display against Youngs Boys would leave United needing to go Spain and beat Valencia in their final Group H game if they were to remain involved in the competition.
United's sluggish start has been attributed to Mourinho's own approach, which some Red Devils fans feel runs contrary to the club's tradition of attacking football.
But, speaking at his pre-match press conference on Monday, Mourinho insisted: "I want my players to be proactive, not reactive. I want my players to be strong.
"It is not a crucial game, but I want to play like it is the last chance to qualify. I want to play like a knockout game."
Meanwhile Mourinho said Sweden international Victor Lindelof will miss Tuesday's match and possibly much of the busy upcoming Christmas period with a muscle injury.
"He will be out for quite a while. We have (Eric) Bailly and (Phil) Jones. Marcos Rojo has some little injury and Victor an injury -- a proper injury -- that will keep him out for a while, so Jones, (Chris) Smalling and Bailly are the three we have at the time."
"He (Lindelof) has a scan tomorrow but, by the experience of the medical department and the feelings of the players, he has a muscular problem and a muscular problem takes time.
"We need, if possible, every player to be available for that difficult (Christmas) period until the Newcastle match on January 2.
"If we can have Victor available for that period, it will be good."