Doughty was signed in September of 2011. The cap ceiling heading into that 2011-12 season was $64.3M. The cap is currently $71.4M (+11%) but expected to remain flat or maybe fall slightly.
Doughty's numbers coming off his ELC:
08-09: 81gp, 6g, 21a, 27p, 0.33 ppg
09-10: 82gp, 16g, 43a, 59p, 0.72 ppg | playoffs: 6gp, 3g, 4a, 7p, 1.16 ppg
10-11: 76gp, 11g, 29a, 40p, 0.53 ppg | playoffs: 6gp, 2g, 2a, 4p, 0.67 ppg
Total: 230gp, 33g, 93a, 126p, 0.55 ppg | playoff total: 12gp, 5g, 6a, 11p, 0.92 ppg
After this, he signed an 8 year, $7M AAV deal.
Trouba's numbers coming off his ELC:
13-14: 65gp, 10g, 19a, 29p, 0.45 ppg
14-15: 65gp, 7g, 15a, 22p, 0.34 ppg | playoffs: 4gp, 0g, 2a, 2p, 0.50 ppg
15-16: 49gp, 4g, 6a, 10p, 0.20 ppg
Total: 179gp, 21g, 40a, 61p, 0.34 ppg | playoff total: 4gp, 0g, 2a, 2p, 0.50 ppg
I just grabbed the boxcars, but 0.34 ppg / 0.55 ppg = 62%. Not saying it's a straight line relationship of points:salary, but Trouba's definitely been less productive.
You can add in Corsi and PP TOI and maybe you've got an argument that Trouba's a bit closer to Doughty.
Let's be generous and say he's 75% of Doughty.
$7M/AAV under a $64.3M cap is about $7.75M under a $71.4M cap.
75% of that = $5.8M.
80% = $6.2M
90% = $7M