Leclerc started ninth in Saturday's 24-lap sprint, which commenced in intermediate conditions but ended on a drying track.
Amid a split between drivers who stayed out on inters and those who came in for slicks, Leclerc was in the latter camp but admitted he was "completely off the pace" with slicks in damp conditions.
The Monegasque dropped to 12th at the finish, 50 seconds behind Red Bull's winner Max Verstappen.
"At the moment, I'm struggling like crazy whenever it's half dry, half wet with slicks, I'm just completely off the pace," Leclerc said.
"So, we need to understand because now it's three races in a row that we find ourselves in those conditions and I keep struggling.
"I always seem to do something wrong with my driving style that doesn't help the car, and that makes me lose confidence. Then, I'm just really struggling.
"So it's a shame, but I will work harder than ever in order to be stronger in those conditions as soon as possible."
Source: Autosport