Valdes will miss the remainder of the season after tearing his anterior cruciate ligament in the 3-0 win over Celta Vigo last week.
As a result, the Spanish international might have played his last game for Barcelona as the veteran goalkeeper prepares to leave on a free transfer at the end of the season.
"Losing Victor would be significant for any team," Busquets told reporters.
"It's the worst thing in football. We can only encourage him and hope he's with us as soon as possible."
Jose Pinto will deputise until the end of the season.