Smith skated into the zone and passed across to Luca Cagnoni, who beat Florida goalie Akira Schmid five-hole from the left circle at 3:14 of overtime. It was the 21-year-old defenseman's first NHL goal (10th game).
Macklin Celebrini had three assists, and Mason Marchment scored in his debut for the Sharks, who were playing their season opener. Yaroslav Askarov made 23 saves.
Eetu Luostarinen scored twice for the Panthers, who were coming off a 1-0 overtime win against the Carolina Hurricanes in their season opener on Tuesday. Matthew Tkachuk also scored, and Schmid made 29 saves in his debut with Florida.
Captain Aleksander Barkov left the game at 8:07 of the second period after going down awkwardly while battling for the puck in the right corner during a power play. After getting up, he immediately asked for the Zamboni doors to be opened and threw his gloves down on the floor while walking to the dressing room.
The 31-year-old forward was playing in just his second game for the Panthers this season after missing all of 2025-26 because of a right knee injury he sustained in the first day of that season's training camp. He had surgery the day after the injury to repair his MCL and ACL.
Defenseman Gustav Forsling was a late scratch due to an upper-body injury.
Marchment put the Sharks up 1-0 at 14:20 of the first period. He got the puck along the right boards, curled above the circle and scored with a wrist shot through traffic that snuck under Schmid's pads.
Marchment signed a five-year, $33.75 million contract with San Jose on July 1.
Smith pushed the lead to 2-0 with a short-handed goal at 5:52 of the second period. Celebrini stole the puck from Tkachuk, skated in on a 2-on-1, and passed over to Smith for a wrist shot that beat Schmid over his blocker from the right circle.
Smith scored his second goal of the period on the power play to make it 3-0 at 10:37. Celebrini's wraparound attempt was stopped by the diving stick of Schmid, but Smith was able to poke it over the goal line before the goalie could cover it.
Luostarinen scored his own power-play goal at 17:10 to cut the lead to 3-1. Aaron Ekblad's shot from the point went off Askarov's blocker to the right, where Luostarinen swiped it in off the post with his backhand.
Luostarinen was credited with his second goal at 5:01 of the third period to make it 3-2. Dmitry Kulikov's shot from the point hit off Luostarinen before then deflecting in off Cagnoni.
Tkachuk scored 17 seconds later to tie the game 3-3. Sam Bennett stole the puck from Michael Misa along the left boards and sent a backhand pass to Tkachuk, who beat Askarov glove side with a shot off the post from the slot.
