Rennie's side claimed second place in their Champions pool with a 27-24 win over Ronan O'Gara's La Rochelle in France.
Former Manawatu flanker Callum Gibbins (pictured) scored one of Glasgow's three tries in an effort that won praise from Rennie for the quality of defence.
"I thought our defence in the closing stages was outstanding," he said. "We showed a hell of a lot of character to hang in there and our big men did a great job around our maul defence to deny them.
"When we needed to be desperate to prevent them from scoring we were so I'm really pleased with that.
"This result shows we can win ugly and it puts us right back into contention in this pool although there's still a lot of rugby to be played," he said.
Boyd said the 16-43 Champions loss to Leinster was a reminder of the need to be able to take another step up in the upper levels of the competition.
Boyd said when Northamption had held Leinster to 16-19 at the break, "I looked at the guys at half-time and it looked like there was a fair bit of juice taken out of their legs.
"That chat was good but you can tell when guys are fresh after 40 minutes and you can tell when guys have been under the pump," he said.
Two tries to Leinster in the first few minutes of the second half made the difference, even without first five-eighths Johnny Sexton who suffered a knee injury in the game that could possibly keep him out of the Six Nations Championship.
"It's a learning for us that there's another level of physicality and fitness required if we're going to compete with team like Leinster," Boyd said.
"If you look at the European competitions there are three or four or five sides who can genuinely take their game to Test-match level and Leinster are one of them.
"What they bring is this enormous level of physicality which you have got to deal with. There are only three or four sides who can bring that," he said.
Fullback Charles Piutau celebrated his contract extension with Bristol by getting among the try scorers in the 37-11 bonus point win over Stade Francais in Bristol.
Lam said the game had been a case of 'job done' as they had gained the five points they needed as they had blown the same sort of opportunity a week ago.
Having claimed the win, Lam set an immediate goal of another five-point win in Paris next weekend as that would mean Bristol had qualified for the playoffs well ahead of time with the only goal remaining that of ensuring they finished top of their pool for home advantage.