Agreed Nathan actually had some very good games for the Tigers this year but also had a year with a few injuries.
Broad is super versatile and integral to the set up, he along with Grimes are a major factor in the fantastic defence over the past 2 years due in simple part to their versatility and ability to roll off for each other and free up Vlastuin and Rance when needed.
Broady was likely carrying an injury at seasons end along with plenty of others and had been dealing with back spasms after getting poleaxed against the Kangas standing his ground when the Kangas had a run on.
Dusty leg/groin, Chimpa leg/knee, Lambert ankle, Graham shoulder, Rance foot, and also George knee are others that immediately come to mind. The side had bashed itself up over 22 weeeks and was near cooked.
None of Balta Markov or Garthwaite will replace Broad in the side imo for simple reasons.
Markov is more a wingman, Garth is a KPP, and Balta is a KPP/Ruck..
Markov will be in competion with Bobble, Basha, Short, Grigg, Grover, Naish, Menadue and Turner for a game he aint going to push Broad out he is not as flexible or strong and he cant play tall at AFL level either.
Balta if they are looking for someone to pinch hit in the ruck isnt going to play in the backline.
Garthwaite isnt a pocket player or flanker he doesnt have the running ability.