But the smoothness with which the 18-year-old has settled into a relegation dogfight nearly caught even Trevor out.
"The last few weeks have been a bonus, unexpected perhaps, but we knew he was coming through and he came in after that 6-0 at Manchester United when it was really a case of 'it can't get any worse'," he says.
"It has been a matter of timing, and the defence had been struggling to keep clean sheets. There hadn't been consistency in that position, both Christian Dailly and Steve Lomas had been playing there, but he has slotted in perfectly.
"Ever since he has come in his temperament has been good, and the back four has become stronger with Rufus arriving as well.
"There has been a stability to it and Glen looks like an established member of the side."
It was only a matter of months ago that his meteoric rise took him from the youths to the reserves and then to the first division, on loan with Millwall - and he took it all in his stride.
"He had some decent games at Millwall, and that Nationwide experience helped him move up to the Premiership," says Trevor.
"He is one of that hardcore of young players that we are looking to keep at the club, a nucleus of young, homegrown talent, that, with the right additions, can really help the club."
Glen, of course, had to handle both the experienced, in players like Kevin Campbell, and the prodigious, in Wayne Rooney when they came on for Everton on Saturday - and he did both with his unruffled style.
One memorable vignette saw Rooney off the blocks down the flank, but he soon had Glen pulling up alongside.
"It was such a good result to get a clean sheet - with Glen's help - at Everton. They have been prolific, and it demonstrates how confidence is getting higher," concludes Trevor.
Let's hope confidence is still high on Sunday, April 27, the new date for our penultimate away game of the season against Manchester City at Maine Road.
It has been switched from the previous day to a 2pm kick-off, as it is now on Pay Per View TV.
Around 2,000 tickets will be available for the game from Thursday, while the home game with Sunderland and the trip to Bolton Wanderers are both sell-outs.