The American international played our glamour friendlies against Celtic and Lazio and held onto the number one spot for the Premiership opener at Everton on Saturday.
Kasey had little chance with the Toffees' goals in the 2-2 draw but was typically dominant in his area throughout.
Asked why he went with Kasey, boss Glenn responded: "Kasey finished last season for us, played the last seven games and did very well.
"Probably going to the World Cup and the fact that he trained, even though he didn't play, meant he came back looking very sharp.
"I've got two very good goalkeepers, international goalkeepers, experienced goalkeepers that I can call on.
"What I want at this club is competition for places and I want to be able to rotate a little, certainly up front where it's the hardest part of the game to play and play over a long season.
"With what I've just said, at least at one end of the pitch I've got that pressure to perform which I think is healthy for any club."
Meanwhile, Glenn said that Goran Bunjevcevic's new role as the anchor man in midfield in a 4-4-2 system was all about balance.
He added: "We've got Steffen Freund still out and Steve Clemence hasn't started pre-season because of an Achilles problem.
"One thing we learned from our midfield in pre-season was that our balance wasn't right and if you don't get that right in the hub of the your team you are on offer at this level. Goran has had to play in there and done very well for us."
Glenn Hoddle has explained his decision to go with Kasey Keller in goal ahead of Neil Sullivan.