Johnson explains Willis substitution and admits concern over defender

Lee Johnson admitted he is concerned about Jordan Willis' fitness after the centre-back came off injured during the 2-1 defeat to Plymouth Argyle.

Willis has been managing a long-term issue with his patellar tendon, and the hope was that an injection administered in the latter weeks of Phil Parkinson's tenure would see the 26-year-old through the rest of this campaign.

A heavy Stadium of Light pitch clearly did not help the centre-back on Tuesday night, and Johnson says he will have to be carefully managed through the next few weeks.

"It's a concern for us," Johnson said.

"He's obviously got a sporadic patellar tendonitis and it can come on at random times.

"He reminds me a bit of Paul McGrath, who basically had to just not do anything and then play.

"We can't do that forever, but while [Tom] Flanagan is out and we're a little bit short in that area, he's going to have to nurse it and play the minutes he can."

Willis' latest setback was all the more frustrating given his standout display at Plough Lane on Saturday afternoon.

The centre back had been superb as Sunderland absorbed pressure from AFC Wimbledon, and Sunderland's head coach had afterwards hailed the return of a player with 'Championship level' attributes.

"He's so quick, he's like a rolls-royce," Johnson said.

"I feel like he's still chasing a bit of fitness, I was thinking about bringing Dion

on towards the end.

"But you see the sprints, the recovery, the burst of power, it's Championship level minimum, that power.

"We do need to work on his base fitness but it also comes down to recovery, a powerful player like that is going to need an extra day to everybody else if you want to keep him playing games."

Injuries have left Johnson struggling to settle on a regular back four.

Denver Hume will be absent for eight weeks with a hamstring problem, while Flanagan is unlikely to return until the end of the month and Conor McLaughlin is likely to be out for around four weeks after hernia surgery.

Luke O'Nien is closing in on a return, having been on the bench for the last two games.