"It gives them plenty of time to make sure they're on top of their game."
The 39-year-old Drysdale has been well off the pace since returning from his sabbatical last year, losing his most recent encounter with Manson - at last month's North Island Championships - by over 13 seconds.
Cotter remained confident Drysdale was slowly getting back to his best.
"That's what's going to happen over a period of time," Cotter said.
"He only got back in the boat in August.
"It takes time to get back to your peak again, and that's where he's progressing steadily - Mahe has won three Olympic medals, is wise and knows what he can do."
The rowers will also face off at the nationals on Waikato's Lake Karapiro next week but Cotter won't be reading too much into the results.
He said he was thinking longer-term, towards the World Champs.
To get the day's top sports stories in your inbox, sign up to our newsletter here