The Nigerian international has been a mainstay in the Baggies back line ever since arriving in a £2million deal from Rotherham in July 2019.
But the defender had to make do with a place on the bench for Albion's first four Championship outings under new head coach Valerien Ismael.
After an injury to Matt Clarke, Ajayi was restored to the starting line-up for the trip to Peterborough. And he responded in style by netting a 94th minute winner.
And now he is back in the team he is determined to stay there.
"I had to get my head around not being in the team," Ajayi said.
"Then it was a case of working as hard as I possibly could to be ready when I did get my opportunity.
"I looked within and made sure I was the best possible version of myself so that when I was called upon I could give my best.
"Now it’s all about showing what I am capable of."
Despite having only made one start so far, Ajayi is thoroughly enjoying playing under Ismael.
"Things are going really well under him," the centre-back continued.
"The thing’s the manager asks from the team are things I feel I bring to the team anyway.
"He is very intense but in order to get his philosophy across, he has to be.
"Everything has worked perfectly since he came in."
Ajayi was part of the Albion side that was relegated from the Premier League last season.
But they have responded to life back in the Championship really well, with Ismael's side unbeaten so far having taken 13 points from their opening five games.
"Everyone is hungry to do well and show last season was a blip," Ajayi added.
"We want to get ourselves back in the Premier League.
"We have got a very, very, long way to go. We are taking things one game at a time. But we are pleased with our start."