Ryan Trevitt has had his loan spell cut short by injury.
The 20-year-old joined on a season-long loan from Brentford and made 20 appearances, scoring five times, but suffered a serious injury in December.
Grecians boss Gary Caldwell said: "We are gutted - Ryan has suffered an injury that will keep him out for a significant period of the remainder of the season."
"He has been in fantastic form for us and has created some memorable moments since joining, scoring the winner at Burton Albion and two incredible goals against Middlesbrough during our fantastic Carabao Cup run."