They played very, very different roles, so it is extremely hard to compare them.
Leddy had one of the hardest, most shutdown defensive roles in the NHL this year. He played the 7th most 5 on 5 minutes of all NHL D men with a 36% O-Zone start rate. He played the 6th-most minutes against top competition of all NHL D men (which was 39% of all his minutes). For the 2nd year in a row, he and Parayko had arguably the hardest job of any pairing in the NHL. Despite that, he managed to be the only D man in our top 4 with a positive goal differential at 5 on 5 (+1 while all our other top 4 D were -8 or worse) while all his underlying metrics were right around the rest of the D group. He played 10 minutes on the PP and 212 minutes on the PK and finished the year with 3 goals and 28 assists, with all but 1 point coming at even strength or shorthanded.
Chychrun logged big minutes at 5 on 5 (11th most), but Zub and Sanderson played the shutdown role while Chychrun got deployed in a slightly offensive role and middle-of the road quality of competition. He played about 130 fewer minutes against elite competition as Leddy (which meant only 31% of his minutes were against that top competition). He had positive possession numbers, but they were worse than the rest of Ottawa's top 4 group despite playing an easier role. His goal differential at 5 on 5 was -24, which was by far the worst on the Sens. He played 18 minutes on the PK and 219 minutes on the PP. He finished the year with 14 goals and 41 points, with 16 of those points coming on the PP.
Chychrun's usage was easier than the usage we gave Krug this year. He had better underlying metrics than Krug, but pretty similar results.
There was no proof of concept that Leddy could handle the role we have him in prior to us acquiring him. He has done so much better in the role than I expected. Maybe Chychrun would too. But nothing about his metrics or career so far suggests that he would be a good fit for that role. Realistically, a Chychrun acquisition would likely be a direct replacement to Krug's spot in the lineup right now or a complete overhaul to the way we deploy our D pairs.
Edit: Every time I look at Leddy's stats I am blown away at how well he has played as a shut down D man. He and Parayko have been paired together and handed arguably the league's hardest workload for 180 games now and Leddy is exactly even at 5 on 5. I keep expecting the results to fall off a cliff and they just never do. I don't think his skillset is at all suited to his current role, but he just keeps performing admirably.
