He provided the pass which initiated a superb break in the lead up to Connacht's only try of the game, touched down by the 20-year-old Eoin Griffin.
Both McKeon and Griffin hail from Galway, as does flanker Andrew Browne, who featured in the build-up to the try. All three are Ireland underage internationals and have bright futures ahead of them.
Pleased with the youngsters' progress, Connacht head coach Eric Elwood said: "To be fair, I thought Eoin McKeon had a terrific game.
"Andrew Browne was outstanding, he was prominent in attack, prominent in defence and I think he's really stepped up to the plate in the last couple of weeks.
"(Eoin) Griffin did really well on the wing as well. It's great to see that, they're three of our own young lads so that's really positive. We've always said that if they're good enough, they'll get their opportunity."
Elwood's charges are facing into their third game in the space of 11 days. This Thursday sees them clashing with the Newport Gwent Dragons at Rodney Parade.
"Obviously we were disappointed with the Leinster game, we did a lot of good things in the first 20 minutes but we didn't take our chances," added the former Ireland out-half.
"To have only three points after all that, if we had gotten the try it would have put a very different complexion on the game so we're disappointed.
"We felt that by our standards, and with our defence this year they (Leinster) got easy enough scores but they took their chances well.
"Now we travel to the Dragons, obviously they'll be smarting from their defeat over here at the start of the season so we're expecting a backlash. It'll be a difficult task for us, it's always difficult over there."
The last five meetings of these two sides have all been won by the home team on the day. Connacht won 40-17 over the Dragons in round 1 of this season's league, but have not achieved a season's double over the Welshmen since the 2007/08 campaign.