In Barclay's absence Fusaro has made a flying start to the RaboDirect PRO12 season, making five starts and playing a pivotal role in Glasgow's fantastic 23-19 away win against European champions Leinster.
And the 22-year-old is confident that, with the Heineken Cup kicking off next month, there will be plenty of opportunities for him to build on his impressive early showings.
"Obviously there is competition for places at openside and even more so now that John is back," said Fusaro, who recently signed a two-year contract extension with the Warriors.
"But that is what you want at any rugby club and when you look at the next quarter, we have 13 games to play, including six in our Heineken Cup pool, so we are going to need everyone available.
"Although I have made a decent start my feet are firmly on the ground. The opportunity to train with and learn from the likes of John is one of the big pluses for me. It's up to me to make the most of that."
Fusaro counts the victory at the RDS Arena over Leinster as the greatest achievement so far in his fledgling career but admits there remains plenty of work to be done both as a team and individually.
"To have started and played in the victory at Leinster is something I will always remember," he added.
"The fact they had not lost in 28 games at home, including against some of the best in Europe and we ended that run with such a young side was fantastic.
"I was rested for the trip to Cardiff but to rattle in four tries in Wales was a superb performance. What was great about that was we backed it up by beating the Dragons to get our first home win.
"When you look at how strongly we finished the first quarter and take into account we have our Scotland contingent coming back ahead of the Ospreys game then we are in particularly good shape.
"But there is no way we're going to get carried away. We are handily placed but now we need to build on our recent form."
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