The Kiwi revealed he had 51 fit players at his disposal this week with only four – Adam Ashe, Oli Kebble (both ankle), Pat MacArthur and Leo Sarto (both shoulder) – on the injured list.
Nevertheless, he has chosen to omit Scotland regulars like Alex Dunbar, Huw Jones and Ali Price from his 23 and rewarded the players he believes are in the best nick and done much to get Glasgow to this home semi-final against the reigning champions.
Centres Nick Grigg and Sam Johnson get the nod, with Peter Horne on the bench, and Rennie explained: “It’s about form. In our opinion, Nick and Sam have been our best midfielders throughout the year.
“Sam is really good with ball in hand, he’s got great feet and he’s a punishing defender and a good communicator. He’s had a great season.
“Nick is quick and dynamic in attack. He’s a good chop defender.
“There’s not a lot between all these guys. We’re fortunate we’ve got really good depth in midfield but we felt, based on the opposition, that they’re our best fit.
“We’ve picked the best team possible based on who we are playing. It’s tough and it’s to the credit of the guys left out that they’ve taken the disappointment well, have worked really hard and helped the other guys prepare.”
Jones has so far failed to replicate his often stellar displays for Scotland in a Glasgow jersey since his mid-season arrival and Rennie believes Grigg and Johnson are the best combination to go up against Scott Williams and Hadleigh Parks. “They [Scarlets] have a reasonably big midfield with Hadleigh Parks there and Rhys Patchell at 10, who is very good at challenging the line,” said Rennie.
“We need to make sure we’re strong defensively there. Both Sam and Nick are very good ball carriers with the ability to get behind the defence and create quick ball for us.”
The team is not far off the one that lost 26-8 away to Scarlets last month as Glasgow experienced a bit of a late-season dip.
“Attitude is everything. We came up short that day,” admitted the coach.
“I thought we played really poorly post-tackle and we knew that would be important as they have so many guys who are good at stealing pill [ball]. They did a good job that day in denying us possession, but we were a little bit lacklustre, so everyone has to be on it [tonight].
“It’s a no-tomorrow scenario if we don’t get it right. We’ve prepared well and the attitude has been great. I would expect a far better performance.”
Glasgow went on to finish the regular season with defeats at Ulster before heading into a three-week lay-off ahead of tonight’s match but Rennie refuses to emit any sense of concern.
“Even if we had won those games we would still have had the weeks off,” he said. “So you could question that. But we’ve learnt a lot from the past month. It has given us time to tidy up parts of our game and it’s given us a chance to freshen some of the boys up. They were pretty jaded going into that final game [against Edinburgh].
“From a training perspective it has been excellent this week. The boys are really sharp, we’ve got full tanks. We’ve had a long time to prepare tactically for what’s going to be required. We feel we are in a good spot.”
Rennie predicted a fierce battle between the two No 8s, and best friends, Ryan Wilson and John Barclay, who returns to face his former club.
“We’ve turned around John Barclay’s photo upstairs… no that’s not true,” said Rennie with a smile. “Obviously I’m sure he’ll be welcomed back here and he’s got a lot of good mates in our team but I’m sure they’ll put aside that friendship for 80 minutes and rip into each other I’d imagine.
“He and Ryan ripped into one another in Llanelli. They’re good mates so I’m sure that’ll happen again.
Tonight is the kind of occasion which tempted one of New Zealand’s most highly regarded coaches to make the move to Scotland and he admitted he was feeling a particular buzz this week as kick-off approaches.
“Yeah, I have,” he said. “The We Are Warriors signs all round the town and so on. There’s lots of energy, lots of people we’re bumping into, the people who watch rugby over here are really excited to have the game in Glasgow and we want to put on a performance that highlights that. We’re looking forward to it.”