New Senators goalie Pascal Leclaire stopped 14 of 16 shots in Ottawa's 3-1 loss to Florida in both teams' preseason opener Tuesday night.
Scott Timmins and Kamil Kreps put Florida ahead in the first period and David Booth added a goal in the second.
Alexandre Picard put the Senators up 1-0 on his shot from the blue line through traffic to beat Florida goalie Scott Clemmensen.
Ottawa played without stars Daniel Alfredsson, Jason Spezza and Alex Kovalev.
Leclaire was acquired by the Senators in March for Antoine Vermette, but had to wait until Tuesday to make his Senators debut after season-ending ankle surgery in January.
The Panthers open the season on Oct. 3 in Finland against the Chicago Blackhawks.