POOR ball use was the main reason St Kilda's three-game win streak came to an end against Sydney at Etihad Stadium on Saturday afternoon, coach Alan Richardson says.

The Saints came into the game on the back of some reasonable form, including a 23-point victory against Greater Western Sydney a fortnight ago.

They held on in the first half to be trailing by 11 points but the scoreboard blew out to 50 by the end of the game.

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"The margin's the really disappointing part. Our footy didn't work today and that's full credit to Sydney. They were too good for us … but it shouldn't be that margin," Richardson said.

"It was that margin because we just butchered the footy.

"Part of that was Sydney, but there was too often that we had players that weren't under pressure and weren't able to execute, whether it was rebound or entry. They scored too much from our own kick from the back and they scored too much from our poor kick going inside 50 and gave themselves an opportunity to get really strong field position."

WATCH: Alan Richardson's full post-match media conference

Losing Jack Newnes to concussion in the first quarter didn't help with that.

The 100-gamer was injured in a fierce contest with young Swan Callum Mills but Richardson said the wingman would likely be fit to face the Western Bulldogs next Saturday.

"Rebound wasn't positive, there's no doubt about that. From back to front, we didn't get through once in the first half. We were a little bit better in the second half. Newnesy's an important player in that, so is Jimmy Webster," Richardson said.

"But we still should have been able to get through. There were times when we had opportunities to go and it was a combination of Sydney were just too strong defensively and we hurt ourselves with our use."

Webster was out after suffering a broken right hand against Carlton last week.

The Saints came under the microscope this week after an ugly sledging incident involving Blues captain Marc Murphy, but Richardson said his side's display wasn't a result of the added scrutiny.

"That would be taking too much credit away from Sydney. They were too strong for us," Richardson said.

"Energy doesn't affect your kicking. It affects your running, your willingness to compete and to fight. We've had 20 extra tackles … it was much more about execution, and Sydney."

Being one down on the bench has a "marginal" influence on the game, Richardson said, but it wasn't the reason the Saints lost.

"Newnes is a massive runner, so that probably has a little bit more of an impact. It was a game that went up and back a little bit. Sydney were trying to hang on to the footy at times, 120 uncontested marks is a reflection of that, so you've got to defend a lot and those runners are really important, but that would be underselling what they did to us," Richardson said.

Newnes is very likely to play next week but injured onballer David Armitage is set for more surgery on his troublesome groin.

"He'd be anywhere between six and eight weeks," Richardson said.