Brawn shocked F1 by turning up at the final pre-season test in 2009 with a car that was nearly a second faster than anything else after a battle to survive following the withdrawal of former owner Honda.
"He's been doing some running on the field in straight lines, but when you've got a knee injury it's twisting and turning that causes aggravation and I think he needs to test it in the county game first, " he added.
Abdessalam Benjelloun was next to test McGregor's goal, with the forward turning and twisting on the edge of the box before seeing his shot claimed by the keeper.
Attempting to hit street speeds, and even turning, seems a bit too risky at this point and after a few test runs, which attract a handful of passersby, the C-1 is wheeled back to its resting place.
North's stunning return on a turning track - which earns him a place on the Lord's honours board - doubled his career tally of Test wickets in his 16th five-day appearance for the baggy greens.