Penrith spoiled veteran backrower Lance Thompson's NRL farewell with a Jarrod Sammut field goal giving the Panthers a thrilling 21-20 golden-point extra-time win over Cronulla at Toyota Stadium.

The Sharks looked set to send the retiring Thompson out in style when they led 20-10 with 20 minutes remaining.

But late tries to Penrith wingers Michael Gordon and Luke Rooney, and a Sammut sideline conversion, levelled scores at 20-all to send the game into extra time.

The comeback was completed when Sammut slotted a field goal five minutes into extra time to steal the win after Sharks halfback Brett Kimmorley thought he nailed a 40m effort seconds earlier only to have the attempt waived away.

Thompson, who returned to the field with three minutes left in regular time after spending most of the second half on the interchange bench, scored his first try in almost 18 months in the first half to give Cronulla a 10-6 halftime lead.

The 30-year-old retired after the match, his 239th first grade game, after doctors told him his dodgy knee had only one game left in it.

Thompson pounced on a Luke Rooney mistake to score uncontested in the 15th minute to put the Sharks up 10-6 after Greg Bird had scored to cancel out Nathan Smith's opener.

When Fraser Anderson scored four minutes after the halftime break it looked like the Sharks could run away with the game, but they failed to put away a stubborn Panthers side.

Penrith began their comeback when Jennings crossed out wide in the 52nd minute.

Several times on the last tackle, Penrith looked like they would be forced into a turnover but they kept the ball alive and Smith fired a lovely cut-out pass to Jennings, who did well to stay in the field of play to score.

Bird restored the Sharks advantage when he powered his way over for his second try of the game in the 59th.

But it wasn't enough to deter the Panthers, with Gordon crossing after a brilliant Rhys Wesser run and then Rooney scoring for his first of the season with just minutes remaining.

Sammut then stepped up under pressure to slot a sideline into a strong southerly in cold and wet conditions at the Sharks' newly-renovated home ground.

Despite the shock loss, the near 14,000 fans stayed to cheer Thompson on a lap of honour after he thanked the crowd.

Panthers coach Matthew Elliott said after the match he knew his young halfback would produce the goods when it mattered most.

"You've actually got to know Jarrod to understand my feelings ... but when it came to getting us back in the game I had no doubt he'd kick it (the sideline goal)," Elliott said.

"He's just that sort of kid, same as the field goal. It was a pretty special effort, two special plays from him."

Elliott was proud of the way his men refused to give in.

"I wouldn't say it was a fantastic performance but it was really gutsy, it showed some desperation in the first half.

"We came up with some last ditch plays to score some tries and I'm just really pleased with the boys, it was fantastic the way they kept hanging in there."

Sharks coach Ricky Stuart and halfback Brett Kimmorley both played down Kimmorley's 40m effort in extra time - most in the stadium had thought it went over.

"I think it went to the right, I was hoping it would come back further but I'm pretty sure it went behind the posts," Kimmorley said.

Stuart was more disappointed about surrendering a ten-point lead.

"We can't afford to be giving eight-, ten- point leads away in game's like that," Stuart said.

"That was a costly game, we didn't do enough in the second half to go along with it."

The Sharks were also lamenting the chance to send Thompson out a winner but the man himself said he couldn't be prouder of his teammates.

"I couldn't be happier to finish with a better bunch of blokes, I've got a lot of mates in this team now which is terrific and something I'll cherish," Thompson said.

"I feel relieved, it was the toughest week I'd ever had to go through."

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