Tell me exactly how exactly you expect 1st year player to master a complicated McCoy scheme with a shitty line and only HALF the reps as any other QB gets in the league AND practicing against the best pass defense in the league?  Lynch needs confidence (he has proven he can make any throw and is one of the most athletic players on the field), and what they are doing will not get him confidence.  
Siemian started all last year AND practiced his first year under Peyton freakin' Manning, then started his entire next year.  It would be incredibly disappointing if he wasn't playing better than Lynch.  Lol