The New Zealand star, who will move to Northampton later this year, suffered what is reported as a torn pectoral muscle in the 60th minute of the match.
It meant he flew back to Wellington on Sunday with his season - and Hurricanes career - likely over.
The Super Rugby final takes place on Saturday, July 6 and it would appear that Proctor won't be available for the Hurricanes even if they make it that far.
"Losing Matty hurts," said Hurricanes coach John Plumtree.
"In my eyes, he's one of the best players in our backline...but we've got some pretty good midfielders around our environment."
Proctor, who is a talented centre but can also play on the wing or at full-back, worked with Saints boss Chris Boyd at the Hurricanes, winning the Super Rugby title in 2016.
And after his switch to Saints was announced back in January, Proctor said: "I am excited to have signed for such a prestigious club in Northampton Saints.
“For a long time now, I have had the ambition of testing myself in the Northern Hemisphere and for so many reasons Northampton is a great fit for me.
“Not only will I have the opportunity to be coached again by Chris Boyd – the person I have worked with the most as a professional player – but I will also have the honour of joining a club that is steeped in tradition and boasts a rich history of success.
“The club and I share the same goals in wanting to achieve as much success as possible on the pitch, while also contributing to the wider rugby community off the field; so overall I am thrilled to be heading to Franklin’s Gardens.”
After making his Super Rugby debut in 2013, Wellington-born Proctor was part of the Hurricanes side that – under Boyd – secured the title three years later.
He celebrated his 50th appearance for the franchise in 2018, while also being named captain for Wellington Lions’ Mitre 10 Cup campaign.
In the same season Proctor then made his All Blacks Test debut against Japan in November, with his representative career also including the Maori All Blacks, New Zealand Under-20s and New Zealand Schools.
And Boyd said: “Matt is exactly the calibre of player that we want to be bringing to Northampton – he’s a world-class talent.
“I obviously know first-hand what he can do having worked with him back in New Zealand, and I am confident he can slot into our back-line next year alongside the quality players we already have at Saints.
“At 26, Matt is entering the peak years of his career and he had the desire for a new challenge on this side of the world. We feel that he can really fill his vast potential here in Northampton.”