“I'm totally excited, I just can't wait to get down there and get on the field,” said John in The Times.
“I always felt and knew that there was something inside me that could go further. I knew my own potential and that I could go far, and now that I am lucky enough to have been given that chance I aim to take it with two hands."
Glasgow coach Sean Lineen told the Evening Times: "This is what happens when a player displays real dedication, attitude and application at training.
"It will be a real test for Jon against the Ospreys front row. The Liberty Stadium may be an intimidating arena, but I think Jon is up to it."
John Barclay will miss Glasgow's remaining Magners League fixtures after fracturing a bone in his foot. "John's injury is a massive blow," said Sean. "He has been a huge player for us this season.
"Calum Forrester will shuffle across and I have every faith he can give a good account of himself."
Eric Milligan starts against Ospreys just a few weeks after he'd thought he had finished with pro rugby. Eric returned to teaching after what was effectively a two-year sabbatical with the Warriors. Sean thanked St Columba's High for helping out after Fergus Thomson and Dougie Hall were ruled out.
Dan Parks will miss Glasgow remaining Magners League games. The club investigation has been completed but, with a court appearance due to take place, he won't be considered for the games with Ospreys and Connacht.
Looking ahead to next season, Sean told the Evening Times that he hoped to bring in some new faces.
"We have had a look at a couple recently in Peter Murchie and Dan Van der Merwe, who both impressed," said Sean.
"But, as well as taking into account what these guys bring on the field, they must also be able to fit into the squad off it.
"There are other players who are under scrutiny and we will see how that all pans out.
"We will make a decision on Peter and Dan soon while, of course, there is plenty going on in terms of securing current squad members such as Hefin O'Hare, who has just signed a new two-year deal."