Ciaran Clark

Clark has been on the bench for the last two games.

Benitez has paired captain Jamaal Lascelles and summer signing Florian Lejeune in the centre of his defence.

Clark – who was outstanding during Newcastle’s Championship-winning season – is likely to be among the substitutes again for Monday night’s game against Burnley at Turf Moor.

Benitez had started the season with Lejeune and Clark in his back four.

However, Lejeune suffered an ankle injury in the club’s Premier League season-opener against Tottenham Hotspur – and Lascelles seized his chance after coming off the bench.

Lejeune returned to the starting XI against Southampton earlier this month at the expense of Clark, signed from Aston Villa last summer.

Benitez said: “We have four defenders. (Chancel) Mbemba has been playing as a left-back and right full-back, because we didn’t have players for these positions in some games.

“It’s difficult. I was explaining in an interview before – you have to pick 11 players for the game and seven for the bench.

“So that’s simple. It’s mathematics. You have to leave seven, eight or nine players out.

“If you want to play with three centre-backs, fine – they can all play. If you want to play with two centre-backs and a line of midfielders in front, someone has to go to the stands.

“Because Lejeune and Clark were playing well during the pre-season, Lascelles had to improve – and he did that.

“Jamaal’s now doing really well, so Lejeune and Clark are competing. If Mbemba’s right, it’s four.”

Benitez has spoken to Lascelles, Lejeune, Clark and Chancel Mbemba about the competition for places in defence.

“For me, it’s not that one of them is better than the other one,” said United’s manager.

“It depends on the games. Maybe you have some injuries. One will play, the other will have to wait.

“I was talking with Jamaal, Mbemba, Clark and Lejeune about that. They have to compete.

“They have to be ready, because if tomorrow I say to one of them ‘you’re playing’, but he has not trained well and then does not play well, the fans will say ‘Rafa was right – he didn’t play because he is not playing well’.

“They have to be ready, they have to compete. If you want to play for a top side in the Premier League, you have to be prepared to compete (for your place).”

Meanwhile, England manager Gareth Southgate watched uncapped Lascelles last weekend along with countrymen Jonjo Shelvey and Isaac Hayden.

Asked if 23-year-old Lascelles was ready for a senior international call-up, Benitez said: “That’s a question for him more than for me.

“What I can say is that he’s doing a great job. He’s working every training session really well.

“He’s very committed and pushing everyone in the right way.