Ok, so Bozak missed time from Oct. 26-Nov. 23 and Dec. 5-Dec. 27. Lets look at that first stretch first.
Things started off well as Kadri and Kessel combined for 10 points in the first 2 games. In the two games following that Kadri had a single point while Kessel had 0. That's when the JVR experiment started. To be clear, Kadri had four games on the top line when Bozak was first injured before he was replaced. Kadri went back to the 2nd line before missing 3 because of his suspension. Upon return from his suspension he was put back on to the top line where he scored a goal but Phil was pointless. Kadri was again bumped from the top line after that for a game as Holland played there before Bozak returned. All-in-all Kadri had 5 games on Kessel's line where he put up a total of 6 points during Bozak's first absence.
Bozak's 2nd injury had him out for 12 games, and Kadri was on the top line for all 12 of them. During the first 6 games Kadri had 5 points (Kessel had 7). So at this point we're looking at 11 games and 11 points for Kadri on Kessel's line. It's the last 6 games that everybody remembers though and this is what tarnishes Kadri's record. Kadri had just 1 point and Kessel had 0 at even-strength. A bad stretch, no doubt. But two things to keep in mind are that during this stretch Kadri was taken off the top powerplay unit in favour of Lupul, something that never really happened when Bozak was in the line-up. The other is that Carlyle started to cut Kadri and Kessel's even-strength ice-time in the final 4 games of that stretch, which led to some fun instances where Jay McClement actually played the same or more than those two did at even-strength.
So in 17 games where he played primarily with Kessel Kadri had 12 points, which is a .70 PPG rate. In the 4 seasons prior to last season Bozak scored 134 points in 238 games, playing almost exclusively with Kessel. A .56 PPG rate. Bozak had 4 years of sucking with Kessel before finally having a successful season. If he kept getting another chance there's absolutely no reason we should be writing Kadri off after 17 games.