McFadden, 32, is a free agent after leaving Scottish Premiership side St. Johnstone in the summer and had been training with childhood club Motherwell before joining the Union on trial earlier this month.
The former Everton and Birmingham City forward made a positive impression during his two-week stint in Philadelphia but, having now returned home, it remains to be seen whether he will be back at PPL Park for the 2016 campaign.
Speaking at his weekly press conference ahead of Sunday’s home clash with Orlando City SC, Curtin told reporters: “We’ll sit down at the end of the year after Orlando and we’ll make some evaluation on that. He did a great job when he was in, did everything he could.
“I think he was fit, he played at his highest level possible, so, showed very well for himself. We had a good talk with him at the end and told him kind of where we’re at in terms of our roster; obviously, there’s no flexibility now to sign anyone.
“But, he did a good job in his short time here, everything he could, and we’ll have a discussion after the Orlando game with him about what makes sense moving forward.”
McFadden, who earned 48 Scotland caps between 2002 and 2010, made just 10 starts in his lone season at St. Johnstone due to injuries and suspension but, with his Premier League and international pedigree, he could be an intriguing acquisition for the Union.
Already eliminated from play-off contention ahead of Sunday and likely to finish in ninth-place in the Eastern Conference, the team are in definite need of reinforcements and, while the ex-Sunderland man might not be earmarked for a regular starting role, he could add some solid attacking depth alongside the likes of C.J. Sapong, Sebastian Le Toux, Cristian Maidana, Andrew Wenger, Zach Pfeffer and big-name summer signing Tranquillo Barnetta.
Scottish imports like Kris Boyd, Shaun Maloney, Kenny Miller and Barry Robson have not enjoyed too much success in MLS in the past but, if Philadelphia can work out a deal for the right price, then he might prove worth the investment – as long as expectations are not too high.