De Jong - recruited from Dutch giants Ajax - has spent most of his debut season on the sidelines, with a collapsed lung suffered in February the latest problem, but the Netherlands international moved closer to a return after featuring for Newcastle's U21s on Monday.
The 26-year-old played 73 minutes in a 2-1 win over Aston Villa and his performance has him in line to make the bench against Swansea City on Saturday, with Newcastle bidding to arrest a six-match losing streak in the Premier League.
"I am just glad to be back playing and I even asked if I could play this game," De Jong said.
"I was glad for that and maybe I can be part of the team next weekend. I am training as well so my legs are a little heavy in the game but I think 73 minutes was good progress.
"I feel I am still three or four kilos lighter than I was at the beginning of the season. I need to gain strength, muscle and explosiveness.
"We will see if I can help the team but I need those extra games and extra training sessions so I am working.
"I can't rush it, I don't think I can help the team if I am not at 100 per cent. If I am joining in not fit it won't be good for me or for the team.
"We have to pick the right moment."
De Jong added: "You want to be part of the team and I haven't really been part of the team this season.
"I have mostly been training by myself so it has been quite tough on me and also on the team, the club and the fans.
"They expect a lot from a new signing and then this happened so of course it is most frustrating."
