Arsene Wenger has conceded that he is concerned about the outcome of every game in spite of the level of preparation because the energy levels flowing from player to player changes on a regular basis.

The Arsenal boss revealed that a player may not have the same energy levels on a Monday in spite being at his very best the day before, which would affect his game over the 90 minutes. The Frenchman believes that this has nothing to do with fitness but biology, which plays with the internal dynamics of a player.

He insists that it creates a pang of uncertainty in a player's performance, which can affect the game at a major level. The Gunners boss could be referring to Olivier Giroud's performance against Monaco, when the Frenchman huffed and puffed his way through the game but failed to put his name of the scoresheet, in spite of being handed with multiple chances to redeem himself.

His performance was seen as an aberration on the day because the 28-year-old had otherwise been scoring goals and is among the most in-form players in the league.

"Everybody is different and approaches a matchday differently, but I always try to be confident. I'm always confident that my team will do well and I want to show that," Wenger told Arsenal's official website.

"But you never know exactly the mental energy that will be in the team during the game, nor the physical energy that will be in everybody that day. Why? Because we are all human beings and don't wake up every day in exactly the same state.

"That goes for each of the players as well, so if you multiply by 18, it shows you the uncertainty that can create. So I'm confident but also a bit uncertain and curious as to what kind of mental and physical energy will be in the tank for the team.

"I make sure that everybody around the team fills that tank as much as we can. Of course there is a certainty about the quality of my players but an uncertainty about the energy level that will be available on the day of the game," he added.