The 1 then 8 is not an option.

From the CBA
An SPC with a term of greater than seven (7) years, provided, however,
that a Club may sign a Player to an SPC with a term of up to eight (8)
years if that Player was on such Club's Reserve List as of and since the
most recent Trade Deadline. With respect to potential Unrestricted Free
Agents only, the ability to re-sign a Player to an SPC of eight (8) years
expires when the Player becomes an Unrestricted Free Agent.

This. But also why in the hell would a player of JT's status sign a 1 year deal. What happens if he blows out the knee again next season? Gets a career ending concussion? Everything goes out the window and he's screwed himself out of millions of dollars for the rest of his life.

People forget that these players have limited opportunity to cash out and secure themselves for life. Signing a one year max deal would be about the dumbest thing JT could do. There's too much risk.

Now I’ll quote myself... “Tavares signs a 1 year max contract worth 15.9 million. Then immediately signs a 8 year extension worth 9.5 million. The 8 year extension does not show below.”

He would get a total of 9 years with the leafs instead of 7 by signing two separate contracts on the same day. The first being a 1 year 15.9 million dollar contract. Now, because he is technically in the last year of his contract and he is currently with the leafs he can sign an extension. Then, immediately after signing the 1 year contract, he signs a 8 million dollar EXTENSION worth 9.5 million per year with the leafs. However, the 8 year contract EXTENSION does not show, because CapFriendly does not have the tools to do so.

You completely missed the point of what I was talking about.

No I didn’t I addressed both your concerns in one comment. I’ll restate the day he signs the 1 year contract is the same day he signs the 8 year extension. Meaning if he were to get injured the leafs would still have to pay him for the next 8 years.

No, because the second, contract extension is dramatically less AAV than the initial it is not allowed via the CBA, and he would be forced to go all the way to UFA status before being allowed to do so (1 year later). Thus the earlier concerns apply and there would be dramatic risk all upon Tavares.

In any case, why would Tavares sign with Toronto in any case? He is supposedly interested in winning the Cup and clearly both Tampa Bay and San Jose are in a much better position to do so both long-term and short-term, offer much better quality of life, would not be living in a fishbowl and, at least in Tampa's case, have a much higher take home pay with zero state taxes?

Since he was not on the leafs as of the most recent trade deadline he cannot sign an 8 year deal/extension. This would mean he cannot sign a 1 year deal and then an 8 the same or next day.