Garside, who predominantly plays at scrum-half, started on the wing in the exhibition game at cinch Stadium at Franklin's Gardens.
And his day was to end with a standing ovation as the Saints supporters showed their appreciation for his incredibly energetic showing during the 48-12 defeat.
Garside made some key defensive interventions while also showcasing his speed and fast footwork in attack.
And Saints boss Dowson said: "Jake was 21 on Friday and so as a birthday present, he got a standing ovation.
"He was outstanding and he is incredibly tenacious, aggressive, absolutely rapid and we're looking at him as someone like Cobus (Reinach), who can play nine and on the wing.
"He had a great season last year coming off the bench for Bedford, and we wanted to give him an opportunity to start on the wing and show what he's capable of.
"He can definitely do a job.
"He's got a fantastic attitude, he's desperate to succeed, desperate to get better and he's got a real edge to him.
"He's not the biggest of men but he's desperate to get involved, he hits and he chases back.
"And you can't defend speed!"