Amid speculation that the Dallas Stars were going to take a run at improving their goaltending position this summer, the team wasted no time by trading the fourth-round draft pick they received from Montreal in the Jordie Benn trade to Los Angeles in exchange for the negotiating rights to pending unrestricted free agent Ben Bishop.

Bishop is coming off a rough season split between Los Angeles and Tampa Bay, but has been among the league’s best goaltenders for the few years previous. That means Bishop will come at a steep price should he sign with the Stars, further complicating the large percentage of the cap the Stars are currently spending on goaltending.

At 30 years old, Bishop isn’t likely to be in a big decline yet, but he’s not in his prime anymore either, which is another factor when you consider he will likely want some term on his last major contract opportunity.

Keeping in mind that both Kari Lehtonen and Antti Niemi have seen steep declines in their levels of play in their early 30s this kind of move isn’t without risk. So does Bishop actually supply a substantial enough upgrade on Lehtonen and Niemi to justify the financial risk here? The Stars are already spending $10.5 million on goaltending next season, though you’d expect them to move one of the other two goalies if Bishop hangs around.

To find out what kind of upgrade Bishop represents, we can break down each goaltender’s save percentages by zone, compared to the league average numbers. First, let’s take a look at what expectations for saves are from each zone:

As you can see, shots from outside the slot have a very low chance of going in, while shots from the high slot are nearly three times as dangerous as shots from the perimeter, and shots from the inner slot or red zone are about six times more dangerous. To put it very simply, your average shot on net from the perimeter has a 3.76 per cent chance of beating a goaltender, while the high slot improves that to an expected shooting percentage of 12.3, and shots from the inner slot are expected to beat goaltenders 22.8 per cent of the time.

It follows then that goaltenders who face tougher shots will have lower expected save percentages, which is where we can start to truly define goaltender talent.

Almost half of all goals in the NHL are scored from the red zone or inner slot, meaning it’s easily the most important area for goaltenders, and it just so happens it’s the area with the least variance overall, meaning good goaltenders will consistently be above average there, even if other areas fluctuate.

Keeping that in mind, let’s compare the last two seasons from Lehtonen, Niemi and Bishop.

A year ago Bishop was among the elite in the NHL at his position, and though he dropped off pretty significantly in the high slot this season and gave up more soft goals, he was actually even stronger in the high danger area, which would suggest his poor season might be a bit more of a mirage than a true drop in performance.

Undoubtedly there are things he needs to work on in the off-season, but that high danger save percentage is an encouraging mark.

As for the other two goalies, Lehtonen actually had a decent season in regard to high danger chances, but as has been the case for the past couple years, he has been prone to giving up weak goals from the perimeter. He gave up more goals from the point than Niemi over the past two years, but he’s also stopped the tougher shots at a much higher rate.

Niemi has been a very weird goaltender overall, as he’s very strong on shots from a middle distance, especially on his right side of the ice, but he’s extraordinarily porous from close range and seems to be trending in the wrong direction there.

To make matters worse for Niemi, while he didn’t give up many more soft goals than expected a year ago, he started to struggle a bit more on perimeter shots this season.

Lehtonen makes $1.4 million more than Niemi does next season, so even if he’s the superior goaltender it may make less sense for the Stars to keep him. Lehtonen’s numbers might hint that he’s still a decent goalie though, and for a team that plays a tighter game than the Stars it may be worth the risk of taking on his $5.9 million.

If the Stars are able to pull off a trade to move either goaltender, signing Bishop looks like a slam dunk move, though they will need to reign in salary and term as much as possible. They’ve been down this road too many times to make the same mistake again.