The most stunning trade of trade deadline 2021, in many ways, has its roots in a deal that was consummated almost two years ago.

When the Carolina Hurricanes agreed to absorb the final year of Patrick Marleau’s contract, carrying a $6.25 million AAV, in June 2019 and the Toronto Maple Leafs forked over a 2020 first-round pick in return, that set the new pricing for what we like to call “getting the hell out of salary cap jail.”

And that was in a pre-pandemic world.

Since then, the flat-cap environment has caused GMs to value their cap space like never before.

“I was able to witness it first-hand last offseason, but cap space is more valuable now throughout the league than it probably ever has been before because it’s so rare,’’ Tampa Bay Lightning GM Julien BriseBois said to me last month.

And yeah, he felt it all right. The Bolts had to offer up a 2022 second-round pick to Ottawa in a trade involving other players and contracts on the eve of training camp in late December to help fix their cap problem. But the cut line was a second-round pick for cap relief.

This brings us to Monday’s fun hockey deal involving Detroit and Washington: The Red Wings sent Anthony Mantha to the Capitals in exchange for Jakub Vrana, Richard Pánik, a first-round pick this year and a second-round pick in 2022.