ST KILDA coach Alan Richardson says a more mature and professional David Armitage is the reason behind the 26-year-old's stunning start to the season. 

The midfielder is arguably in career-best form, and was crucial to the Saints' historic come-from-behind win over the Western Bulldogs on Saturday at Etihad Stadium. 

Armitage had a career-high 45 possessions (16 contested), eight clearances, five inside 50s and kicked a goal in the Saints thrilling seven point win. After six rounds, he is averaging 33.5 disposals per game, the best figures in his 113 game career. 

WATCH: Armitage simply sublime

He has also grown as a leader, captaining the club against the Magpies in round three in the absence of skipper Nick Riewoldt. 

Richardson said Armitage had stepped up following the retirement of champion midfielder Lenny Hayes. 

"Dave has had a really impressive start to the year," he said. "He's sensed the opportunity to be the man. 

"He's matured as a footballer and as a young man. He's a real pro now and he's reaping the rewards. 

"He's lost a significant amount of weight. He's not only able to win the ball on the inside, but he's able to give us some good run on the outside." 

Armitage, along with youngster Jack Billings, led a resurgent Saints side to victory on Saturday. 

WATCH: Billings comes up big

The Saints were 55 points down early in the third quarter but remarkably turned their game around to win by seven points. 

Richardson said the win showed the playing group was growing in self-belief. 

"I hope it explains growth," he said. "I hope it shows this group has some belief, we’ve only really had one really disappointing performance this year. 

"I have no doubt that our players sense that the journey we're on is heading in the right direction. I didn't predict that what happened in the second half would transpire. 

"But what I do think it shows is that this group does believe. And that belief is still a little fragile but it's certainly gaining momentum each time we play."