If I'm not mistaken, it was shortly after Nishikori turned pro in Oct 2007.
Yes, that's about right.
Keep in mind Glenn's been living at Nick since he was 14, lol, he nearly married Nick's daughter...so he's been with Nick for 20 years.
Glenn also spent lots of time with Boris Becker when Boris was at Nick, they were great friends Glenn and Boris...and of course Glenn and Tommy Haas are best friends.
I reckon Glenn could still be playing doubles and doing very well, him and Tommy Haas were a great team, and Glenn and Rick De Voest had some great results together...but when Nick offered him the opportunity to coach Kei he decided to go for it...good move, IMO.
Glad to see Kei has so many fans around here.