The Australia international signed for the Scottish Premiership club in January following the expiry of his contract at Shandong Luneng in the Chinese Super League.
The 25-year-old former Hearts defender managed 12 league and five cup appearances last term but is now expected to really show what he can do in the coming campaign.
“It was difficult for us in January for different reasons,” McNamara said.
“You can’t go out and spend a lot of money to replace players, and you’re relying on players getting up to speed quickly.
“Ryan McGowan’s season had finished in China.
“Some can hit the ground running and some take a pre-season.
“The two fullbacks in particular (McGowan and fellow January arrival Paul Dixon) have been excellent in pre-season. They’ll be like two new players.”
McGowan filled in for the injured Ivan Franjic for Australia at the 2014 FIFA World Cup but wasn’t named in the Asian Cup-winning squad and missed the Socceroos’ opening World Cup Qualifier against Kyrgyzstan in June.
Football Federation Australia