Shortly after his appointment as head coach, Bilic revealed he had a word with Harper after being disappointed with his performances in training.
The midfielder immediately upped his game and forced his way back in the first-team fold.
And after hailing him as Albion’s ‘best player without the ball’ during the win at Sheffield Wednesday, Bilic is delighted with the progression his young midfielder is making.
“Rekeem is one of the players who has made the biggest progress since lockdown, and before lockdown as well,” Bilic said.
“In the beginning, he wasn’t consistent.
“He was showing glimpses of his talent and ability, but not all the time.
“Even before the lockdown, when we had some suspensions, or injuries, when Romaine (Sawyers) was suspended - I didn’t have any doubts about putting him in the team.
“Rekeem had started to play really well, he had started to train consistently – power, movement, tactics, stamina, skill, everything.
“He’s becoming more and more mature.
“I never denied that I love him as a player - I love those kind of players, who are powerhouses but can pass the ball, that’s great.
“He’s in a good way, let’s be honest, but he cannot stop, he must keep working.
“It’s also my job to keep him like that.
“If he continues to show what he’s been doing recently, then he’s got no limits.”
As well as being pleased with Harper, Bilic also had praise for Kamil Grosick as he prepares to take on former employers Hull tomorrow.
The Poland international is yet to start a game for the Baggies since his January move with his eight appearances having all come from the bench.
But Bilic said Grosikci is closing in on his first start – and he said he would have got it sooner if it wasn’t for Albion’s impressive form shortly after he arrived.
“He’s there – it’s a thin line,” Bilic said when asked if Grosicki is pushing for a starting spot.
“Maybe if his papers came on time, he’d have started the game against Luton.
“He skipped that game and then we went onto Millwall, and then to Bristol City andbang. That’s why he had to wait.
“He’s played almost every game, but he hasn’t started.
“He’s done well for us, considering he’s a new player and his first games have been coming from the bench.
“The first couple of games he wasn’t involved, but that was because of the competition - you can’t put them all in.
“Now he’s had his chance. I think that when he came off the bench at Sheffield Wednesday he was really good.
“He played enough minutes to put a marker, a stamp on the game.
“He was very hungry, he was active. He was taking people on. He was exactly what I wanted him to be.
“He gained a big plus for that game, and now he’s much closer to starting a game than he was.”