Rennie addressed Mo'unga's availability following the All Blacks' 50-19 victory over the Vodacom Bulls at Loftus Versfeld on Saturday, their third win on South African soil after earlier triumphs against the Stormers and Hollywoodbets Sharks.
"He arrived late last night. He is very, very excited and jumping out of his skin," Rennie said. "He's already done a fair bit of study, and we'll spend the next wee while him getting his head around our game. We won't pick him in the first test. He will get a chance to get some game time against the Lions."
Ruben Love appears set to wear the number 10 jersey for the Ellis Park encounter, with Rennie indicating the Test side will "look a lot different to the team tonight." Hooker Codie Taylor, who scored twice in the first half in Pretoria before a planned half-time withdrawal, is likely to feature in the run-on XV.
The tourists have endured a difficult injury run, with George Bell, Proctor and Caleb Clarke all sent home. Rennie expressed greater confidence over Roigard and Jordan, both of whom he expects to complete a full week of training. "We're pretty confident they are going to be alright by next week," he said. "Both of them, we want them to have a full week of training, but they've certainly ticked enough boxes."
McKenzie's prospects remain less certain. "Damian is the other one who we are probably less confident about, but we still think he has a good chance to play on the weekend," Rennie added. "We'll get a little bit into him tomorrow, and then hopefully he'll train well on Tuesday. The expectation is that all three of those guys will be available."