It was not, he reflected, as though they did not have their chances. They had most of the ball in the second half but after winning the penalty count comfortably in the first period, their discipline disappeared and, with it, their chances.
“It was always going to be tough,” said Rennie. “They were missing two guys to international footie, we have 23 guys missing this weekend. It is a bit of experience missing.
“We talked about being more direct. At 15-5 we should have made a statement and we had another bust that we should have scored off, but we played too much of the game in the middle third of the field, going sideways and turning over too much ball.”
The inexperience was on show from the start as Glasgow gave away a soft early score, messing up a lineout and then allowing the Welsh to pull them wide on one side before hooker Liam Belcher went over on the other.
But Glasgow then took a grip on the match with two well-worked tries. The first came courtesy of George Horne, the scrum-half, who spotted space behind the retreating Dragons maul and chipped into it for Brandon Thompson, the centre, to collect and score.
The second saw Nick Grigg, the other centre, make his third break in quick succession and this time find Horne on his shoulder to run in his eighth try of the season. Adam Hastings, who had failed with his first conversion after his kicking tee went missing, put over the second to add to an earlier penalty.
The Dragons were not out of it, though, clawing back into the game with a Zane Kirchner penalty and then drawing level when Hallam Amos, the full-back, found a mismatch in midfield to break from his own 22 and kick into space for Jared Rosser, the wing, to score.
The second half saw a lot of effort from both sides but nothing resembling a score as they both struggled to get the ball as far as the opposition 22. Not a game to remember.