Others
There's been about 50 players mentioned in this thread and 0 defenders in the bunch.
I'll try listing a few :
- Robert Picard was a #3 overall pick who looked like a future superstar when he scored 21 goals and 65 points in his 2nd NHL season, and was a +3 as the icetime leader on a terrible defensive team in Washington. 7th in Norris voting that year. But his career went down the tubes after that - slumped to 54 points and a -23 the next year, and then turned into a journeyman who never scored more than 41 points again.
- Harry Howell wasn't 'mediocre' but his Norris trophy season was a huge outlier when you look at his career as a whole. The Bernie Nicholls of defensive defenders.
- Dave Pichette scored 57 points one year for NJ and was never heard from again afterward.
- Tracy Pratt was a career journeyman who turned in one brilliant All-Star season in 1974-75 in Vancouver.
- Jim Schoenfeld was a good player, but his 1979-80 season where he went +60 and finished 3rd in Norris voting behind only Robinson and Salming was a pretty big outlier.
- Ron Stackhouse was a decent enough player who scored 35 points almost every year of his career aside from two seasons where he scored 60 and 71 points and was one of the highest-scoring defenders in the game.
- Randy Carlyle's Norris season is a no-brainer here. Not really a 'mediocre' player, but it's still bizarre he won the Norris.
- Doug Lidster set the Vancouver Canuck single-season defensive record with 63 points, but never scored more than 38 before or after that.
- Darren Veitch was a huge talent with personal problems who put his game together for one huge season in Detroit in 1986-87. The Jacques Richard of defenders.
- Paul Cavallini finished 7th in Norris/All-Star voting in 1989-90, then quickly regressed back to journeyman status.
- Dan McGillis played at a level in 2000-01 that he would never come close to touching in the rest of his career.
First re Robert Picard. Think Jacques Richard, Bryan Fogarty.
Other d-men.
Tom Johnson during the 1958-59 season whem Harvey was hurt. Throw in Bob Turner the same year.
Jean -Guy Talbot after Harvey was traded.Harry Howell type year.
Dave Burrows with the Penguins.
Bob Woytowich with the Bruins.
Hy Buller with the Rangers.
Ian Turnbull had a short spurt with the Leafs, more than one season but way short of a career or prime.Same could be said about Tom Bladon with the Flyers.
Mike McMahon 1967-68 with Minnesota.
Larry Goodenough with the Flyers.
Al Simms with the Bruins.
Yves Racine with Detroit/Philly dollar store version of Ian Turnbull.
Kent Douglas with the Leafs.