Rennie said Donald had been enormously influential on and off the park, surpassing the expectations of most commentators in his 11 appearances this season.
"He's been great for us," Rennie said. "You know what you get from Beaver - he's going to ask some questions of the defence, he's going to run hard.
"I thought he was fantastic [in Cape Town] and that was the reason we brought him back.
"He's contributing nicely, whether it's at 10 or 12, and he'll be involved in some way in our next game."
Donald and the Chiefs were due to arrive home in Hamilton in the early hours of Tuesday morning.
Their travel-heavy play-off path mirrors last year, when they beat the Stormers in a Cape Town quarter-final, before falling 25-9 to eventual champions the Hurricanes in a Wellington semifinal.
Rennie says they won't over-think their approach to recovery, believing the key to being physically ready for the Crusaders was quickly returning to regular sleep patterns.
"We're going to come home and make sure we do a better job than last year," he said. "Do we make the guys sluggish by too much analysis and so-on?
"At least we're in New Zealand. It'll be nice to spend some time in our own beds."
