The defender has been in outstanding form for the Baggies ever since Allardyce replaced Slaven Bilic as boss back in December.
But the Dudley-born chief wasn't as pleased with the talented centre-back when – as a youngster– he decided to leave Bolton for Arsenal back in 2007.
Allardyce was in charge of The Trotters at the time and had hoped Bartley would remain with the club.
"Strangely enough, I had Kyle when he was a very young player," Allardyce said when asked how impressed he has been with Bartley since taking charge at The Hawthorns.
"When he was a schoolboy he was at Bolton Wanderers and Arsenal bought him when he was 16.
"I wasn't very happy with him at the time but they paid a bit of money for him.
"Now he is coming to the age I think where his experience and his quality is standing out.
"He is a good talker and a good leader and we all know there aren't many of them about these days.
"That defensive unit has been – and will continue to be – the backbone of helping us get out of trouble if we are to do so.
"We have got a little bit more hope after beating Chelsea but it's still going to be a very difficult task."
Bartley's impressive performances in recent months have led to admiring glances from elsewhere with Burnley and Newcastle reportedly keeping tabs on the 29-year-old.
The defender put pen to paper on a three year deal when he joined Albion from Swansea on July 2018.
But the Express & Star understands the number of games he has played this season has triggered a one-year extension meaning he is now contracted to the club until the summer of 2022.