Sunderland defenders set to undergo surgery this week

Graham had missed the last two games with a knee issue, but the scans suggested that there was no major problem and the striker returned to training at the start of the week.

The 35-year-old took a knock in Monday's session, which Johnson says will have to be assessed.

Sunderland's head coach is likely to rotate some of his side for the visit of Plymouth Argyle, to ensure full fitness during what is a hectic fixture schedule.

"We have a couple of knocks that you always get in games," Johnson said.

"So it may well be that there one or two changes for this game, not so much through injuries but through freshening it up and "making sure that for the next game, we're fully fit as a squad."

On Graham, Johnson added: "Danny had his scan and it was good news, there wasn't an awful lot showed up.

"He did go down in training today, but seemed to be OK on the physio bed.

"I'm a little bit worried about it we'll have to see how it settles over the next couple of days."

Luke O'Nien is unlikely to return to the starting XI, despite making an earlier than anticipated return to the matchday squad at Plough Lane on Saturday afternoon.

The Black Cats are closely monitoring the 26-year-old to try and minimise the risk of him suffering a recurrence of the dislocated shoulder that has kept him out of the majority of Johnson's tenure so far.

O'Nien's versality gives Johnson some welcome variety on his bench, having already confirmed that he intends to make full use of the fan favourite's versatility.

"It would have taken a lot to put him on the pitch.

"He's still growing in confidence, we were at the point where we felt we needed that option [from the bench] for five or six minutes in a couple of roles.

"It's got to come from Luke with this injury, it can't come from me or the physios.

"He's got to be in a position where he feels confident it's not going to recur.

"Luke is always wanting to work hard and is always demanding, which I like.

"He's an interesting character and my type of personality, that's for sure."

Lynden Gooch will be absent from the matchday squad after testing positive for COVID-19 on Friday.

The 25-year-old remains asymptomatic and the Black Cats are hopeful that he could return to the squad for the trip to Ipswich Town next Tuesday.

Johnson also confirmed that Conor McLaughlin and Denver Hume will undergo hernia surgery this week.

Hume has already been ruled out for six to eight weeks with a hamstring issue.

"Both Conor and Denver are having an operation in London on Tuesday," Johnson said.

"Denver is obviously nursing a hamstring injury as well so it's probably the best time for him to have the hernia operation.

"The prognosis will depend on what surgery they go for, but we hope Conor won’t be any longer than three-and-a-half weeks max."