SYDNEY SWANS spearhead Kurt Tippett and Carlton's Ed Curnow have both been substituted out of a brutal semi-final at ANZ Stadium well before half-time.

There was some suggestion Tippett had carried a knee injury into the game and he then came off second best diving for a contested mark in front of Blues defender Michael Jamison.

He sprayed his set shot badly from directly in front, 30 metres out, and then limped from the ground heavily favouring his right leg.

Swans doctor Nathan Gibbs assessed Tippett on the bench and he then had long discussions with the club's fitness staff and did the odd jog to see if he could run it out.

He initially had a bandage put below his right knee, but he was then quickly put into the substitute's red vest and was replaced by Lewis Jetta.

It is a double blow for the Swans, who have now lost their main key forward and have been forced to use Jetta – who is playing just his second game since round 10 – much earlier than they would have hoped.

The situation could be worse for the Swans, with Tom Mitchell then helped from the ground 19 minutes into the quarter with a right ankle injury.

Mitchell attempted to return during the second quarter but was soon confined to the bench again.

The Blues have also been forced to throw their sub Tom Bell into the game midway through the second term following a medial injury to Curnow's right knee injury.

The knockout final now looms as a real war of attrition with both sides using their subs so early in the game.
 
The winner of Saturday night's match will face Fremantle at Patersons Stadium in a preliminary final next week, while the loser can start planning for 2014. 

Carlton's Ed Curnow watches on after being subbed off with a knee injury. Picture: AFL Media
 

Twitter: @AFL_JD