I based that opinion on multiple categories between the two players when at even strength.
Schenn had higher values in shot-attempts against (So both Corsi and Fenwick), expected goals against, actuals shots against, scoring chances against, and high danger shot attempts against. I disregarded offensive contributions (which would be to Schenn's betterment) and only looked at metrics against the Blues with both players on the ice. I also broke down the two players ice time to account for if they were paired together vs. not. Their metrics were putrid together, but Kyrou's improved dramatically when moved away from Schenn and Schenn's stayed closer to the numbers when they're together. The major difference between the two was Kyrou's results were significantly worse than the predictive values while Schenn's were significantly better than his predicative values. So Kyrou was on the ice for more goals against than Schenn. In terms of play, Kyrou was playing better defensively than Schenn was last year but the results went Schenn's way.
Broken Down:
| TOI | Average TOI / TOI per Game | Corsi Against/60 | Fenwick Against/60 | Shots Against/60 | Scoring Chances Against/60 | Expected Goals Against/60 | High Danger Corsi Against/60 | Goals Against |
Kyrou With Schenn | 397:13 | 5:01 | 63.44 | 48.64 | 35.65 | 35.19 | 4.88 | 14.5 | 40 |
Kyrou Alone | 791:34 | 10:01 | 57.83 | 43.96 | 30.85 | 32.97 | 3.16 | 13.72 | 54 |
Schenn Alone | 839:49 | 10:14 | 63.23 | 48.44 | 34.58 | 35.08 | 3.37 | 15.22 | 43 |
All metrics are based on Even Strength and the metrics are labelled "/60" to denote a per 60 minutes basis while any other metric without are counts unless labelled otherwise. All numbers are found on Natural Stat Trick. I highlighted the worse number between the two as red.
So yeah, it's not hard to say that Schenn was worse defensively than Kyrou. Neither were good and both need to find a way to improve their overall affect on the game. But, if anything, Kyrou's faults were always under a microscope because his results were worse. Doing any sort of research would point to other players playing, at least, equally bad defensively but just walking away unscathed more frequently. I wouldn't say Kyrou was unlucky, more so others were luckier.