Given the way the cap has been the past few years, his relatively injury-free career, and his relatively young age, to me, the bigger threat is that teams would would give him a longer term to bring down AAV. Of the older RFA and UFA guys (25+) who got 4M+ contracts:
Samuelsson 7
Weegar got 8
Sanheim 8
Sergachev 8
Cernak 8
Lindholm 8
Letang was 35 and got a 6 year deal!
Reilley 8
McAvoy 8
Pulock 8
Parayko 8
Nurse 8
Hamilton 8
Pietrangelo 7
Pelech 8
Krug 7
Brodin 7
Jones 8
Josi 8
Falk 7
Spurgeon 7
Morrissey 8
Almost all those guys are much bigger names than Zub. I don't see him fitting that echelon.
Only a few guys in their mid 20's got short deals (1-3) year like DeAngelo, Schultz, Barrie, Klingberg and Zadorov. Mostly odd-ball contracts where guys are rebuilding value.
You don't see a lot of -5 year contracts. Toews, Oleksiak, Larsson, Murphy, McCabe, and Ristolainen are the only ones I found who got them in their mid-to-late 20's almost all of them were defensive defensemen though.
Chiarot, Leddy, Ekholm, Martinez, Tanev, Gudbranson, Muzzin, Petry, Brodie, and Manson and others who got 4-5 years each were all over 30. Which makes sense they would ahve gotten 6-8 year deals had they been UFAs in their 20's but were just too old or not good enough to get them in their 30's.
Personally, I still think Zub's situation is closest to guys like Toews, Oleksiak, Larsson, Murphy, McCabe, and Ristolainen. which are all in the 40-5.1M range and 4-5 years.
If we gave him 4.5MX5 years that seems right on the money as far as market goes.