This is the typical on-ice results for the bottom 25% forwards in 5v5 TOI per 60 minutes. Each dot represents 30 players in order of Corsi%. It shows how better Corsi% players, even on the fourth line, tend to have a better relative goal differential than those who do not, with a pretty significantly relationship...
However, it also shows the marginal returns from better 4th line players. The spread of these forwards is between +1 to -8 over the term of a season, or 9 goals to a team's overall goal differential. On average 3 goal change to a team's differential equates to one point in the standings and therefore 6 goals equates to a win.
Chris Thorburn is not a very good 5v5 player. This season he hurt his linemates possession more than all but 18 players in the NHL (looking at those with 41+ games played). His bottom 20% of 4th line + depth players Corsi% (~43%) over the last three seasons places him at about a -5 effect on goal differential in value. In all likelihood, the actual effect is more sever since Thorburn plays in front of one of the worst starting save percentages in the NHL.
Overall this effect on the standings is very little, at least in a vacuum. Thorburn likely costs the Jets about 1.8 goals more than the average 4th line player or 1 goal more than the average depth player. He costs about 1.3 goals more than the average if you combine those samples. This isn't overly huge. About 1/3 2/3 of a point in the standings on average. Big deal.
However, nothing happens completely in a vacuum.
The biggest reason I have issues with this signing is that it isn't necessary. Like Ondrej Pavelec or Mark Stuart, Kevin Cheveldayoff could have signed a replacement level player easily for far less money and term, which means less risk. The Jets already have superior fourth line players in Eric Tangradi, Jim Slater, and Eric O`Dell. In addition, Peluso can fill any #grit role that is needed. Even further, the Jets have Carl Klingberg pushing for a fourth line role.
So why is Thorburn needed? All he does is hold a roster spot for three years when he wasn't even needed. Thorburn walking away likely made the Jets a better team. It was that simple.
Gary Lawless reported that the Jets are likely looking at a 65 million internal cap. Looking at the most likely contracts for Michael Frolik, Michael Hutchinson, and Eric O`Dell, that leaves the Jets with about 10 million dollars to replace (and hopefully upgrade) the losses of Olli Jokinen and Devin Setoguchi.
Now the Jets have invested 1.2 of that 10 million to Thorburn. That 10% can be the difference between signing a Frolik calibre player over a Setoguchi.
In a league with so much parity, every dollar and minor edge counts and is magnified.