McArdle, who received a late call-up to the Northern Ireland squad on Thursday for their double-header against the Portuguese and Luxembourg, watched on from the bench as Ronaldo grabbed a match-winning hat-trick for the European giants.
After falling behind to a Bruno Alves volley, Northern Ireland equalised through West Bromwich Albion defender Gareth McAuley later in the first half.
With Portugal down to ten men following Helder Postiga's dismissal just before the break, the hosts then actually took the lead seven minutes into the second period thanks to a goal from Derby County's Jamie Ward.
Things took a turn for the worse for Michael O'Neill's side just past the hour mark, however, when Northern Ireland were reduced to ten men themselves thanks to Chris Brunt's second bookable offence.
Ronaldo took centre stage from this point, netting twice in quick succession to put the visitors back in front of the match.
Northern Ireland's hopes of getting back into the match took a further blow when substitute Kyle Lafferty's red card saw them go down to nine men.
With the one-man advantage now in their favour, Portugal sealed all three points seven minutes from the end when Ronaldo grabbed his hat-trick thanks to a well-taken free-kick from outside the box.
McArdle and Northern Ireland will now set off to Luxembourg on Sunday for their next World Cup qualifier on Tuesday (10 September 2013).
Following the qualifier, The Bantams defender is due back in England Wednesday evening.