Hasn't been done yet. The closes anybody has gotten was Sebastian Giovinco 22 goals 16 assists (2015). There have only been two players to register 20 assists in a single season Carlos Valderrama 26 assists 1 goal (2000) and Sacha Kljestan 20 assists 6 goals (2016) Carlos Vela 20 goals 12 assists with 13+ games to go.
Why is Vela able to tear the league up like this? He really hasn't had too much success anywhere else...
He's not the only one to have very good MLS seasons, that didn't have much success else where (Josef Matinez, BWP, Sebastian Giovinco, Ignacio Piatti, Miguel Almiron).
I guess I am just interested in why a long standing goal scoring record is suddenly being shattered in consecutive years... Is the league getting more uneven or something?
The league is getting better every year, those players are surrounded by some good players and when they have a chance they do a good job finishing their chances. Oh I think the forwards and midfielders are a bit better than defenders.
And specifically, the quality gap between attackers and defenders is widening, most likely by design. The TAM and GAM rules were designed to give the star players enough quality help to generate more opportunities, but not to spread the cap around so much that it goes to destroyers and players that don't sell tickets.
With 26 minutes still to go in the LA/NY game Vela has a goal and a assist, giving him 23 goals and 14 assists . Edit: Make it 1 goal and 2 assists (23 goals and 15 assists)