Jens Berthel Askou says Motherwell have to win the battle before the game at St Mirren on Saturday.
Danish boss Askou expects a very different game in Paisley to their league opener at home to Rangers, which ended in a 1-1 draw on Saturday.
Askou anticipates a strong, physical tussle at St Mirren, but also be fully tested, against a side that pushed Celtic close before losing 1-0 on Sunday.
He said: “We finished the game on Monday, in terms of watching what we did well and what we need to improve, and we know this week’s game is going to be a very different type of football game.
“We face an opponent who has some very different strengths, and methods, and approach to the game as Rangers would, which will give us some other challenges.
“That means we’ve tried to prepare for