The result marked the second win on the Ibrox club's pre-season American tour.
But the Frenchman's injury took the shine of an improved performance by McCoist's men.
He appeared to be in a lot of pain as he received treament at the side of the pitch.
And it comes after the man he replaced in today's team, Richard Forster, suffered a
hamstring injury in Saturday's match against Sacramento Republic.
The manager made 10 changes to the team that won on Saturday as he continues to hone his players' fitness ahead of their first competitive match in 14 days when they face Hibernian in the Petrofac Training Cup.
Only Marius Zaliukas retained his place in the line-up.
This morning's game was played in bright sunshine and it was Calum McGregor who put Rangers ahead in the 10th minute.
Ian Black made an immediate impact on his return to the starting XI by setting up McGregor's first goal of the tour.
Indeed, the former Hearts midfielder was the architect behind most of Rangers' attacking moves.
But they failed to build on their early lead and were stung when the Americans levelled the tie.
Winger Cam Hundell, a constant threat down the left flank, held off a challenge from Darren McGregor to beat Steve Simonsen with a composed finish at the near post.
The equaliser galvanised the hosts, but Rangers regained the initaive and came close with a Zaliukas header.
And they edged in front again when Gallagher's long-range effort shot from distance was spilled by keeper Brandon Watson and Clark slid in to roll the ball into the net.
The tempo of the match dropped in the second half as the high temperatures took hold of both teams.
But McCoist still handed run-outs to Barrie McKay, who came on for Faure, Andy Murdoch, Kris Boyd and David Templeton.