The Indigenous star was the Kangaroos' best player in the first half on Saturday at Marvel Stadium, where it looked like Gold Coast were going to win easily.
Simpkin finished with 29 disposals and kicked a goal as North stormed back to secure a memorable six-point win.
He came into the season with a lot on his mind. Simpkin lost the captaincy after unsuccessfully seeking a move in last year's trade period.
Then on January 2, Spicer died from a medical episode. The Indigenous player managed 12 games for North before he was delisted in 2023.
North coach Alastair Clarkson was rapt for Simpkin after Saturday's game.
"That hit Jy pretty hard, as it did all our footy club. They were blood brothers, those two," Clarkson said of Spicer.
"When we weren't going so great in the first half, he was our best player.
"I was so proud of what he stood up for, because it was the Sir Doug Nicholls Round and for 'Spice', he was wearing his number on his footy boots.
"It just meant so much to him."
Simpkin has not missed a beat this season, despite the circumstances around his failed request for a trade, and Clarkson said he remains one of North's most important players.
"It goes underestimated a little bit, just the burden you have when you're a leader at the club - your club and team haven't gone so well for a period of time," Clarkson said.
"The personal weight that burden has on any individual - in a lot of instances that's the coach, but in a lot of instances it's the captain."
Clarkson noted that early this season, Simpkin had unselfishly taken on some run-with midfield roles.
"When he's able to do really sacrificial roles for his team like that, it gives you a strong indication that they're in boots and all. He's certainly that way," Clarkson said.
While veterans such as Simpkin, Jack Darling and Caleb Daniel are not officially in the player leadership group, Clarkson said their standing in the team was critical.
Clarkson also heaped praise on Darling, who kicked three goals.
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