Everton manager Carlo Ancelotti admits his switch to playing three central defenders is an "emergency" situation imposed on him because of injuries.
"I think it's an emergency because we have two important players in Coleman and Digne out. It is only for this reason," he said.
"We have the quality in the squad to play also with three centre-backs, because we have a lot of good centre-backs, but I think it's a moment.
"The fact that we can play with three or four is good for us."
Despite the absence of Digne, who could be sidelined for up to three months after surgery this week, Ancelotti chose not to play his only naturally left-footed defensive player Niels Nkounkou against Marcelo Bielsa's side.
The Italian said the 20-year-old still has things to learn after leaving him out of his squad altogether.
"Nkounkou was not in the squad because I have 11 players, I decided to put Iwobi on the left. The squad is really big," he added.
"He's still young, he needs more experience, he needs to work more. But I am honestly satisfied for what he is doing.
"He will have time in the next game because we have a lot of games. The fact we played with two midfielders (as wing-backs), I think we have good cover because usually the two midfielders have the help of one of the centre-backs to cover the position behind them."
Having enjoyed the best start to a season in over 100 years, Everton are currently in a slump of just one win in their last six matches.
With the likes of Chelsea, Leicester, Arsenal, Manchester United and Manchester City to play in December the trip to Turf Moor is significant for a variety of reasons.
"Of course the result was not good against Leeds, but it was an open game. We want to stay attached to the top of the table so it will be important to have a result tomorrow," said Ancelotti, who will mark his one-year anniversary at the club on Boxing Day.
"This season, there is a lot of competition in front. We are still in front, we want to stay attached and prepare well for the second part of the season. We are where we want to be in this moment."