1) Bryan Murray was not a new coach (came in 81-82)
2) Riggin was not a new goalie, and his stats improved substantially (15-20%; played 20+ games in 81-82)
3) Stevens was poor defensively, particularly as a rookie, because he tended to go out of place to make a hit
4) The rest of the defense was still AHL quality at best.
5) Jarvis did get credit (see: Selke)
6) None of this denies the 100+ goal swing btwn MTL and the Caps.
7) You forget that the Caps traded out their #1 dman (Rick Green), as well. At a minimum, this would offset the acquisition of Engblom.
8) The impact of Langway is particularly noticeable in the PPG allowed category, as mentioned previously.
1) True, but this was his first full season with an off-season to prepare.
2) Riggin was new to the Caps. Parro seems to have been a lesser goalie, as he still let in goals in limited action for the 83 Caps.
3) Scott Stevens may have jumped out of position for a hit, but he was still good overall. An all-rookie selection, 25 points, and a +14 rating aren't bad stats for a #3 d-man. +14 is better than Langway's Even, and in 1984, Stevens would be better.
4) Only if you believe #3 is true. Langway + Engblom + Stevens is a fairly solid top three. Theberge was better than AHL. He wasn't an all-star, but SOMEONE on defence had to help on the powerplay.
Veitch was solid, but missed most of this period. Guys like Timo Blomqvist and Randy Holt playing at the top of the lineup is a serious problem, but not so bad as the bottom slots.
And if 1984 counts, Larry Murphy turned around that 0-7 Caps team really fast when he came over. Way to save Langway's bacon Larry!
5) Jarvis should get credit. He helped that PK unit too.
6) Langway was a huge part of the 100 goal swing. But so were the other additions (subtractions for Montreal), like Engblom and the Selke-calibre Jarvis who are important in #8. Because Stevens and Engblom showed up, the old 2-3 d-men became 4-5 d-men. So the defense improves overall.
Also, if anyone was AHL-calibre, it was the guys playing on the 82 Caps. The 83 Caps had good health, with 18 skaters playing 60 or more games, and 26 total skaters playing 1 game. The 82 Caps had 11 60-game guys, and 41 total skaters. Fewer injuries means better players developing better chemistry.
A small part of the swing is Montreal's loss of Denis Herron, whose .912 sv%, 2.64 GAA and 3 shutouts led the 1982 NHL. It was a smaller part than the Langway/Jarvis/Engblom trade, but a brief outlier of a performance by Herron in 1982 was a part of it.
7) Engblom was a 2nd team All-Star in 1982, with Langway-like offensive stats. Engblom was not as likely to push you around as Langway was, but he was middle-class family's version of Langway (as opposed to poor man's.)
For 1983, Engblom was better than Green (though not in the long-term.) The loss of Green would be more significant had Langway gone 1-for-1 with Green. But Langway came with help...
8) Langway was a top penalty killer, but he wasn't the only one.
Jarvis/Langway/Engblom were all Montreal imports and all logged a lot of time on the PK for both the 82 Habs and 83 Caps. The difference in PK% for the Habs was a drop from 80.07% to 73.85%. This difference between the teams is not just Langway, but the fact that a solid PK unit was imported to play alongside 1 Caps PK-Forward from the prior season's unit. From the PGA numbers it looks like it was Bobby Gould, who would kill penalties for the Caps for the rest of the decade.
In particular, why do you think that the players who played against him, and the coaches who saw him play against them would be wrong about the value he brought? Both as the best defensive d-man in the league, and as the second most valuable player in the NHL behind Gretzky?
Washington was a horrid team that had never made the playoffs. Langway was the most visible addition to a basement-dweller that was all of a sudden good. They got stronger elsewhere on the blueline, had fewer lost games due to injury, had a competent goalie replace an incompetent one, had 3/4 of a top PK unit to replace an incompetent one, and maintained their ability to score goals under a semi-new coach.
Langway brought plenty of value to the table, and no one should argue that Langway wasn't one of the top d-men in the NHL, but he was still overvalued as voters probably didn't account for factors like fewer injuries and the other new pieces.