GEELONG could without Mitch Duncan for an extended period after the midfielder was subbed out of the Cats' 43-point loss to the Sydney Swans with a foot injury.

Duncan was the Cats' best player in the first half with 16 possessions, but was forced from the field shortly after half-time, and was on crutches for the rest of the night.

Coach Chris Scott was still in the dark on the extent of Duncan's injury after the match but conceded the outlook doesn't look good.

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"It really hurt. Mitch is a really important player for us, and his injury looks relatively serious even at this early stage, so we're not expecting to have him in the short term," Scott said.

"I'm really careful of giving the prognosis when the doctors aren't sure themselves, but we're not expecting him to play in the next couple of weeks." 

The Cats also suffered an injury blow pre-match when star forward Tom Hawkins was a late withdrawal with a glute problem, but Scott refused to make excuses for his side's second half fadeout. 

"I'm not going to lie to you and say that it doesn't make any difference and we can just bring another player in, clearly it makes a difference to our team," Scott said. 

"He's a very good player and one we rely on, but it's not the reason we lost the game."

WATCH: Chris Scott's full post-match media conference

The Swans dominated the game after the main break and kicked 10 goals to two to run away with the win, but rather than focus on the disappointment of the second half, Scott took a positive view on the loss. 

Youngsters Jackson Thurlow and Cameron Guthrie were two of the Cats' best.

"I think it has been like that for the last two or three weeks for us, when the game was really on I thought that our guys that are developing were pretty good," Scott said. 

"We may have run out of legs at the end but I didn't think our inexperienced players were off their feet. 

"Sydney are probably the reverse, their side doesn't change too much, a huge percentage of their team is in the prime of their career, credit to them. 

"In some ways we've got a lot to look forward too given the way we played in the first half. The whole competition knows they're a pretty good team, and I thought it was a pretty good contest for most of the night. 

"The scoreboard blew out a little bit and we're clearly disappointed with that, and we need to play better to compete with the best sides, but it's not all doom and gloom." 

Second-half fadeouts are becoming a constant theme for the Cats this season and Scott said he and his coaching staff had some video analysis to do this week. 

But if they do find the answer, don't expect to hear what it is. 

"To be honest, if I knew exactly what it was, I wouldn't tell you anyway," Scott said.