By Ibrahim Sannie BBC Sport, Ghana

Mensah was dismissed after clipping the heels of Peter Odemwingie

The Black Stars captain was sent off in Sunday's 2-1 quarter-final win over Nigeria after a professional foul on Peter Odemwingie on the hour.

The Rennes defender is set to be banned for up to two matches - ruling him out for the rest of the tournament.

"I think John as one of the five best defenders in the world...that it is a major blow for us," said LeRoy.

With defender Shilla Illiasu not fully fit, LeRoy says the Black Stars will struggle without their key defender and the decision to send him off was harsh.

"You know what a blow Mensah's absence is to us," Le Roy told BBC Sport.

606: DEBATE Have your say on the impact Mensah's absence will have

"John did not make a single mistake in the game and I have seen players not sent off for professional fouls much worse than that.

"But we have got a squad with players who can fill in John's position and make things happen for us."

LeRoy, however, is confident Illiasu will be ready to play for the Black Stars in the semi-final against Cameroon on Thursday.

"Illiasu has made tremendous recovery over the past few days and has been able to train with his colleagues," the Frenchman said.

"I could have used him for the second half in the game against Nigeria, but the (sending off) during the game did not allow me to use him.