Deshaun played 7 games last year as a rookie, and now 9 games so far this year.
Want to see his cumulative stats?

16 games (15 starts); 9-6 record; 311 of 489 (63.6%) for 4088 yds (8.4 ypa) with 36 TDs and 15 INTs

For a passer rating of: 101.7.
That, my friends, is not bad for a first-yr QB.

You'd like to see him cut down on the INTs and in fact he's started to. Last year he was getting 3.9% picked, this year 2.5%. That's around the pctg that Big Ben and Aaron Rodgers threw them at last season; a little behind Flacco & Andy Dalton, who were at 2.4%. Deshaun could stand to continue improving. The top guys last season were in the 1.5% to 1.8% range.

Deshaun also takes way too many sacks. 49 over the full 16 games; his sack rate is 9.1%. The mobile guys tend to take more sacks than the statue passers; and Deshaun did rush for over 500 yds over the 16 games. But he's gotta get that pctg down. The top guys (by passer rating) from last season tended to have sack % in the wide range from 6.4% to 7.7%. Tom Brady was under 6%; Brees, Phillip Rivers and the Bathroom Ranger were under 4%. Cutting down on sacks makes the whole offense a ton more efficient: fewer "and longs".

Nitpicking aside: good lord! Is that a promising rookie "season" for a QB, or what???

Deshaun is 23 yrs old this year. Two years older than Lamar.
(They have similar builds, BTW. Deshaun is listed an inch shorter than Lamar, though 8# heavier.)

Forget Brady - Roethlisberger for the AFC. Mahomes - Deshaun is the matchup now.