The Nigerian centre-back, 28, gave a typically powerful performance in Saturday’s 1-1 draw at Middlesbrough.
The former Rotherham and Cardiff stopper played in a central defensive duo alongside Dara O’Shea.
He joined the Baggies from the Millers in 2019 and has since made more than 100 league starts in Albion colours. Bruce, who took over the hotseat in February, says he has noticed a big step up from the 6ft 4in Nigeria international.
“Ajayi I have to say, he’s improved enormously since I’ve walked through the door,” Bruce said.
“I’ve enjoyed watching him, he’s a hell of a good defender. When he’s like he was on Saturday he’s big, strong, powerful, quick, he gave a mountain of a performance, especially second half.”
Ajayi and O’Shea were Bruce’s opening-day centre-back pairing, with Kyle Bartley a substitute. It remains to be seen whether the boss opts to boost his options in that department before the transfer deadline at the end of the month.
The boss revealed managers can never be happy with transfer business and their squad.
He is content with the improvement made so far this summer and believes getting down to business early to land key targets has already proven worthwhile.
“I keep saying to them my job is to knock the door down constantly, we can never be happy as managers, once you’re happy you get into that apathy,” Bruce said. “We’ve got to improve, I know we’ve improved with (Daryl) Dike, Okay (Yukuslu) and the two (John) Swift and (Jed) Wallace, that’s improved us. If we can do a couple more then I’ll try my utmost.”
The manager added: “We’ve brought them in for that reason. We were short on goal and creativity last year and with those two (Swift and Wallace) in particular have been doing it year-in, year-out in the Championship.
“They’ve both got off to a wonderful start, it’s helped us to have them, all the work Ron (Gourlay, chief executive) has put in to get them in for pre-season with us bears fruits because they’ve been in, got used to the lads and settled into the area.
“They will be a big addition to the club, we have to get Okay up to speed and big Dike and that’s like four new signings for myself.
“It’s been great to have Swift and Wallace with us throughout pre-season, but we’d love a couple more. My job is to keep knocking on the door to see if we can. The big clubs are about to start with their younger players so we have to be aware of that market. We’ll see what we can do to improve.”