The Black Cats won courtesy of goals from Ryan Noble after Scott McDonald marked his return to the fold at Middlesbrough with the opener just after half-time. O'Neill had already made up his mind to get a deal done for McFadden before the Scotland international started yesterday's game against Boro's Under-21s. And the Sunderland boss explained that a fear of a dip in form or injury to either Adam Johnson, who is just returning from a thigh problem, or James McClean has helped persuade him to push for a deal until the end of the campaign.
"James' agent is in America at the moment but I will try to speak to him", said O'Neill.
"Will we keep McClean and Johnson fit all the season? Apart from them we have no real width to see us through."
"James also has Premier League experience and did well for a period. He did well against us last season when he went back to Everton."
"If he gets properly fit he can help us. I think it will be good for him. I would look to do it until the end of the season."
"I'm hoping we can come up with something. It is encouraging."
Right-back Phil Bardsley joined McFadden in the Sunderland team yesterday. The former Manchester United defender has not figured so far this season after picking up an ankle problem during pre-season. But the 27-year-old has edged closer to a full recovery after training with the Sunderland first team squad in recent days, which is three weeks ahead of schedule. Bardsley was not included in the Scotland squad yesterday for World Cup qualifiers with Belgium and Wales, but his international boss Craig Levein was at Rockliffe to run the rule over him and McFadden.
O'Neill has also been encouraged by the return to training of Carlos Cuellar, who could be involved at Manchester City tomorrow, and Wes Brown after injuries. The latter, though, is still some time away from a first team comeback. When Cuellar and Brown do make an appearance in the Premier League again they are likely to have a goalkeeper at the top of his game playing behind them.
Belgium's Simon Mignolet has been outstanding so far this season and his good work has not gone unnoticed by his manager, even to the extent that his growing bravery has drawn comparisons with Pat Jennings and Peter Shilton. O'Neill played with both Jennings and Shilton, two of the world game's great goalkeepers, during his playing days and is seeing signs that Sunderland's No 1 is growing a similar toughness between the posts.
"Simon has been fantastic for us", said O'Neill.
"Parts of his game he wants to improve on but I tell you he is as brave as a lion. He made two great saves at Upton Park and two on Saturday against Wigan."
"I must give some credit to the lunatic goalkeeper coach (Jim McDonagh) which has brought that part of his game out."
"He has got stronger looking but I am very pleased with him. He has been splendid. I always compare keepers."
"I took Tim Flowers at Leicester and was fantastic. Kasey Keller too from Millwall and Brad Friedel never missed a game for me. I also took Brad Guzan to Aston Villa who is playing now."
"I like a brave keeper and have seen it since Jennings and Shilton."
Sunderland winger Johnson, meanwhile, has marked his return to fitness with an inclusion in the England squad for the World cup qualifiers with San Marino and Poland.