Gordon has taken part in a series of handling drills this week, and while he was not quite ready for Tuesday's reserves game with Bolton, he could be available for the first team game with Liverpool on September 25.
At the start of the season, it had been expected that the Scotland international would walk back into the side given his strong showings in the second half of last term.
But with Mignolet having impressed in the opening five matches of his Sunderland career, the equation is no longer quite as simple.
The Belgian was one of Sunderland's stand out performers in last weekend's 1-1 draw at Wigan, and Black Cats boss Steve Bruce will face a difficult decision once both of his goalkeepers are fully fit.
I hope the manager has a difficult decision to make now, said Mignolet, who arrived in a £2m summer move from Belgian side Sint-Truidense.
It's not up to me to make the decision, but hopefully I have done all I can to prove I am good enough.
All I can do is work hard and keep performing in the games like I have done. I think I've done okay in the last two or three games so we'll see what happens in the future.
Mignolet suffered a difficult start to his senior Sunderland career, conceding two sloppy goals in the second half of the opening-day draw with Birmingham.
Given his lack of Premier League experience, it was feared he would retreat into his shell, but instead he has responded with a string of impressive displays.
He was integral to last month's 1-0 win over Manchester City, and caught the eye again last weekend as his accomplished performance helped the Black Cats claim a point at the DW Stadium despite playing with a man disadvantage for more than an hour of the game.
With endearing honesty, Mignolet admits he did not know what to expect when he agreed to swap his hometown team for the bright lights of the Premier League, but the 22-year-old also claims it did not take him long to feel at home.
It's always different when you go to another country and you always have to adapt to the style of play, he said.
Here in England, the style of play is very direct.
Before the start of the season, nobody really knew what to expect. If I am honest, even I did not know what would happen.
I gave two silly goals away in the first game, but even after that, I was thinking, I know I can do this'. I knew straight away that I could match the level that was needed in the Premier League.
There were two silly goals, but I felt, This level is the level you can play at if you want to'. From there on, I worked hard, kept my head up and played a few more matches.
Mignolet also listened to the pleadings of his defenders, who asked him to claim more crosses than he had taken in his opening game.
The result was an authoritative display at Wigan, and the youngster is happy to be taking some of the pressure off the players in front of him.
The style of play here in England is different to Belgium,
he said. There were a lot of crosses into the box in the game against Wigan, but I always felt confident. I came for a lot of crosses and held on to the ball as well.
I don't know what the other goalkeepers do, I just try to hold on to the ball because it keeps the pressure off the defence if you can do that. In the first couple of games, my defenders were asking me to do that so I hope I can help them in the box. They said when you keep the ball, you take some pressure off the rest of the team.