With Moray Low moving to Exeter Chiefs and Ed Kalman retiring, Gregor has been strengthening his front row options and today announced the signing of Rossouw de Klerk.
Gregor told glasgowwarriors.org: "Getting a tighthead of Rossouw's quality into the club really adds depth and competition.
"Playing in South Africa is really tough for the forwards as you have some big men out there and he's played over 20 Super Rugby games for the Bulls and the Cheetahs. He's only 24 so there is a lot more to come from him and physically he's in great shape."
Rossouw is the third prop to join the club this summer, after Euan Murray signed up for a second stint and Alex Allan moved west from Edinburgh.
Gregor said: "Euan (Murray) is a Glasgow man and played for the club a few years ago, since then he has gone on to play for some top clubs and become a British & Irish Lion and won a number of caps for Scotland. The position he plays is a lot about experience.
"He is in great physical shape and getting someone in the number 3 jersey with Euan's experience is fantastic for us.
"Jon Welsh did really well for us last season and Mike Cusack, who played a lot of rugby the season before, is coming back from injury and illness, so we expect real competition for that jersey.
"Alex (Allan) has been involved in the Elite Development Programme at Edinburgh and had to work really hard to get into the team there and show what he can do. He's now gone on to win a Scotland cap and has been training really well with us during pre-season."
Scrum-half Murray McConnell was one of the first signings for the new campaign and he'll also be making a return to the club, after coming through the Scottish Rugby Elite Development Programme, while centre James Downey has joined from Munster.
Gregor added: "Murray (McConnell) was involved in our Elite Development Programme and then went away last season and played for Ayr and we then brought him in to train with us for one day a week after Christmas.
"He's always had rugby ability and is a great guy who everyone likes and I think last year showed how much he wants it.
"James (Downey) is a great signing for us. When we heard he was available we acted on it very quickly and it was great to hear he was interested in coming to the club.
"He brings great experience having played at Northampton and Munster, physically he's in great shape, he runs very good lines, he really challenges the defence and is a great tackler, so I think he'll fit in very well."