That's not security. That's just a bad strategic decision.
Only if you care about absolutely maximizing career earnings in a risk-free environment and not balancing the risk and reward as any good agent should.
He took 4x3, so what else was on the table as a two year deal? 3x2? 3.25x2? There's a meaningful difference in lifetime NHL earnings between 6 or 6.5 and 12 million, if he were to never play again.
So let me sketch out for you 3 different outcomes. He's had his ELC everywhere so that money is banked, let's ignore it because it's less than $3M and I'm sure a chunk of it is spent.
1. His knee explodes tomorrow. He can never skate again.
Current contract: 12M
2 year: 6.5M
Net result: $-5.5M but a pretty important 5.5M since he'll have only made ~9M in career earnings.
2. He gets back to his old self over the next 3 years, cap goes up, but he never takes the next step. Signs a max length 7M contract as his next. Plays until age 36 but he's washed after the 8 year so he makes 4M per season.
Current contract: 12M + 56M + 8M = $76M in additional earnings
2 year: 6.5M + 56M + 12M = $74.5M
Net: Basically a wash
3. He goes nuts. Sticks on Hughes or Hischier's wing and totally elevates his game, becomes a PPG plus player this year and puts up 95 in his contract year. His defense elevates. He signs for 12M a season ion his next deal. Plays til 36, signing for an average of 10M until then because salaries are way up but father time catches up with us all.
Current: 12M + 96M + 20M = 128M
2 year: 6.5M + 96M + 30M = 132.5
net result: again, who cares? Yeah, he gave up 4.5M but that's in the world where he's had 9 figures of career earnings. That 5.5 in case his leg explodes is worth orders of magnitude more than the 4.5M he'd make in the perfect world.
So, if you think his agent really f***ed it, you're saying it's not about the actual money in year 3 (since that doesn't really matter that much), but about the
timing of signing the next contract. And I think I can credibly argue that the extra year there (and the 1 year less RFA time being bought) probably actually increases the average contract Mercer signs for next time around. 25 year olds aren't hit nearly as hard as the 27 through 30 year olds when it comes to teams aggressively discounting aging curves these days and he'll have an extra year to showcase his peak performance.