The Light Blues got their North American tour off to a disappointing start as goals from Jordan Vale, Ronnie Arguet and Matt LaGrassa clinched the win for the hosts in California.
McCoist handed starts to summer signings Darren McGregor, Marius Zaliukas and Kenny Miller but it was defender Bilel Mohsni, who netted their only goal of the night, briefly bringing the Gers back into the game before LaGrassa capitalised on a mistake from Sebastien Faure to ease Fusion to victory.
Rangers lined up in a 5-4-1 formation as McCoist used the friendly fixture to tinker with his approach but it failed to pay dividends as the SPFL League One champions suffered their first defeat of the summer. McCoist said: “Defensively, particularly in the second half, we were really poor and that concerned me.
“It made me unhappy more than anything. We did have chances in the second half and some very, very good ones which, on another day, we could and should have scored.
“That’s always going to happen. Sometimes you’re going to take your chances and sometimes you’re not.
“But what disappointed me most of all tonight was the level of defending, especially after the break.”
Rangers have spent the last couple of days being put through their paces in California but turned in a below-par performance as Ibrox legend Richard Gough and former director Paul Murray watched on from the stands
at the Ventura College Sportsplex.
The artificial surface, complete with American Football markings, was hardly conducive to free-flowing football and was covered in rubber pellets.
But McCoist has refused to blame the pitch for Rangers’ shock showing as he targets an immediate improvement ahead of their clash with Sacramento Republic on Saturday.
“Unless I wasn’t watching it correctly, it was the same surface for both teams,” he told rangers.co.uk
“Was it ideal? No, but they had to play on it as well. They did that better than we did and that’s the one thing we have to be honest about.
“We’ve had a lot of training sessions after a long trip here but the level of performance in the second half wasn’t good enough.
“I expected better from that team, even with the training they have done. We’ve worked on a few things and we’ve trained the lads hard enough.
“At the same time, we’ve left enough in their legs to play the game. There was slackness about us which I haven’t seen in a long, long time.
“The boys were taking time on the ball when usually they’d be passing it about to each other. We will have to eliminate that slackness.”