Ferguson copped an early blow and played on after he was injected with painkillers but took himself out of the game after 45 minutes.
Olympic has lost 16 players from their first-grade squad last season but also made some high-profile signings.
A victory would see Wells picked to represent Australia at the world track and field championships this year, and put her on track for the 2020 Tokyo Olympics.
The 17-year-old stopped the clock in 10.61 seconds to win it on the line.
Former Wallabies hooker Marco Caputo says victory against the Canterbury Crusaders this week can resurrect the Brumbies season.