Rwandan striker Meddie Kagere scored the lone goal to hand the Englishman his fifth straight win since he took over as Gor Mahia head coach in July.
"It was a tough game as Posta came to the party as I expected and we worked on the dangers they possess," Kerr told the club’s official website.
Kerr however, has promised to work on denying opponents’ space by possessing the ball after K’Ogalo weakness was exposed by Posta Rangers in the second half.
"We lost possession too much and that made Posta Rangers side keep attacking which is something I need to address in training.”
Kerr, who took over from Brazilian Ze Maria, was particularly impressed with his backline in his fifth win in the domestic league.
"We have the three points and amazing credit goes out to the four defenders, our goalkeeper and the midfield for their desired determination and heart not to concede."
But a true test of what the Briton is made of will come on Sunday during a ‘Mashemeji’ derby against AFC Leopards at Nyayo Stadium.