"I thought we deserved something out of it. Probably a game of two halves, with the breeze that was there," he told IrishRugby.ie afterwards.
"The frustrating thing for me is I thought we played great rugby for 30, 35 minutes. It certainly looked like we created enough opportunities to get something out of the game, but I was pleased with the way we played during that period."
Ultimately though, Walsh felt that one or two mistakes did cost them in the end, which St. Mary's were able to capitalise on when they happened.
"It took us a while to settle into it. We got on the wrong side of the referee early on. A lot of our own mistakes we were punished for.
"In fairness, Mary's are a very good side. You can't afford to make as many mistakes as we did, and they punished us accordingly.
With nine rounds of matches still to play in the 2011/12 Ulster Bank League, there are still plenty of points to be gained and dropped in the quest for the major honours at the end of the season.
Walsh believes that the league title is still there for the taking, and that the next four games will go a long way towards deciding who will come out on top come May.
"We're halfway through the league, we're eight points behind. You have to play everybody again, so you can pick up four points. It's a very tight league," he explained.
"There are funny results in it. Lansdowne seem to be going well. Clontarf bounced back with a very good win today as well. Young Munster seem to have dropped off the pace a bit.
"If you look at the teams that are hitting form, you have to play them again. We play Clontarf away, we play Mary's at home, we play Lansdowne at home. That run of four games is going to decide it essentially.
"Having played everybody, I would be impressed with Mary's. They've been knocking on the door for three or four years, and there is a great hunger there."