Walcott is on-loan at Saints from Everton this season.
"I'm happy to work with Theo, he definitely showed it means something to him to play for this club," he said, with Saints fifth in the Premier League.
“You can feel how much he invests working for the team.
“It was good to see how quickly he has adapted to our game, although he can be more clinical. It's important, we must be a team who can play without these players (the injured Danny Ings).
“We did our maximum with the squad we have. I'm very proud of my team because taking something was not easy."