The Edinburgh flanker will win his seventh cap after being named in the starting XV for the EMC Test, the first of Scotland's two World Cup warm-up matches.
Rennie is joined in the back row by number eight Johnnie Beattie and Alasdair Strokosch, with Jim Hamilton named at lock and Graeme Morrison returning at centre.
And although World Cup places are up for grabs, Rennie admits his sole focus on just doing his job..
Rennie said: "It's really good for me to be given an opportunity - I've got to try and perform well and to perform for the team.
"I don't want to think about the World Cup too much now. I've got to focus on this weekend and try and get things right there.
"If I can do that, hopefully the rest will look after itself."
Morrison, likewise, is looking to seize his chance, after being cut at the final selection for the 2007 tournament.
The 28-year-old Glasgow Warriors centre, who missed the RBS Six Nations with a knee injury, is determined to make amends and be one of the 30 players named in head coach Andy Robinson's World Cup squad on August 22.
Morrison said: "I think it's quite a positive thing that I'll be playing in this game.
"I'll get the opportunity to show what I can do on Saturday and hopefully it goes well.
"I'm desperate to go to a World Cup, given I missed out on the last one.
"It still hurts, but I've learnt a lot since then."
Alastair Kellock, who was Scotland skipper during the Six Nations, was named on the bench, with Hamilton partnering Richie Gray at second row and scrum-half Rory Lawson taking the captaincy.
Kellock and Gray were among five players withdrawn from club service by Robinson in preparation for the World Cup.
Ross Ford and Allan Jacobsen have been named alongside Gray in Saturday's team for their first competitive action since the Six Nations, but John Barclay has been left out of the matchday squad, his place going to Rennie.
Scotland's World Cup campaign begins against Romania on September 10 in Invercargill.
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