NOBODY likes an understudy.

In Seinfeld, the loveable Kramer said understudies were the substitute teacher of the theatre world. And let's face it, we all took advantage and goofed around a little more at school when a sub was called in.

I was devastated as a child when I found out world famous wrestler Hulk Hogan was pulling out of a World Wrestling Federation tour of Australia. He was by far my favourite fighter, so I cracked it when his understudy came out and failed to possess the same swagger as my yellow-singleted hero.

I reckon Saturday's game between the Crows and the Hawks has a little bit of an understudy feel to it after serious injuries to Adelaide's Taylor Walker and Hawthorn's Cyril Rioli.

Both guys are capable of putting on a show for the fans, and they are also almost as impossible to replace.

Almost 20,000 fantasy players need to trade Cyril out of their sides considering the seriousness of his hamstring, while more than 22,000 coaches will have to find a replacement after 'Tex' went down with a season-ending knee injury.

Walker had been disappointing in his five games in 2013, with a high score of just 73 AFL Fantasy points against the Brisbane Lions in round two.

He is certainly better than a player who averages a touch more than 60. Similarly priced players up forward include Eagle Josh Kennedy (he has kicked 18 goals in the past two games against this week's opponent the Western Bulldogs) or Geelong's Tom Hawkins. Both would be viable replacements.

Rioli has more currency ($453,400) and could have been picked as a midfielder or a forward, giving you a huge amount of options, including a swag of guys who average more than 100.

However, coaches' fantasy forward half may not be the only concern this week after a huge amount of changes for round six.

My backline has been hit hard this week with Essendon's Dyson Heppell (groin), Carlton's Bryce Gibbs (hamstring) and Bulldog Brett Goodes (suspension) all missing this round, so I will have to use a trade to make sure I avoid a dreaded zero.

Thankfully my midfield is going swimmingly, with nice scores from the younger brigade last week, including 115 points from Jaeger O'Meara, 98 from Brad Hill and 111 from Sam Mayes.

Mr Fantasy's trade recommendations
Ins:
Dean Terlich (Melbourne), Jonathan Simpkin (Hawthorn)
The Demons have had a horror start to the year, but they will be keen to keep new blood like Terlich in the side. A spot in the seniors is secure if he can go well against the Blues this week (his fifth game this year). Simpkin also showed good signs in the Hawks' pre-season matches, and Rioli's absence may give him nice game time within their midfield rotations.

Outs: Bryce Gibbs (Carlton), Taylor Walker (Adelaide)
I doubt the Blues will be rushing Gibbs back from a hamstring niggle, so I would trade for another gun like Grant Birchall or Beau Waters. If you already have both of those, Hamish Hartlett or Heath Scotland could be the go.