ESSENDON's impressive 5-0 start to the 2013 season has been built on adding a tougher defensive edge to its renowned attacking game, coach James Hird says.

"The most pleasing thing for us is the defence, to be able to defend throughout the game," Hird said after the Bombers' 46-point win over Collingwood at the MCG on Anzac Day.

"There were periods today where we didn't defend properly and Collingwood got a good run against us, but this team has worked a lot on defending and if we don't do it properly we'll get scored against.

"But I thought today to keep Collingwood to 75 points was an outstanding effort by the players."

Sitting alongside Hird at Thursday's post-match press conference, Anzac medallist David Zaharakis said the Bombers's pre-season focus had been on ensuring they worked just as hard defensively as they always had offensively.

"We've always been a team that can score quickly and our offensive attributes have always been our strength but now it's our defence," Zaharakis said.

"Hirdy and the coaches have worked hard over the summer on developing a defensive game plan and you can just see it out there, the first talk you hear is about defence rather than how we attack.

"It's always about how we can defend better. So now definitely the players are really starting to drive it and it's showing.

"You see a bloke split out from a pack and there's a guy just screaming at you to go get them and without even thinking now we're doing that."

But Hird stressed the Bombers remain a defensive work in progress and will pay for any drop off in their intensity.

"Let's not get carried away. We've played five games, we've defended reasonably well, but as soon as your intensity and your actions around defence drop off you can get scored against very quickly," Hird said.

"To be part of a win again on Anzac Day is very, very special. We're not tyring to undersell that, but it's early in the year.

"And we saw last year what happened to us halfway through the year when we didn't get our players out there to train enough and we didn't get to practise what we wanted to practise enough and we got a few injuries.

"We understand where we're at and we've got to keep playing the right kind of football."

Hird said the Bombers' ability to cover for injured key-position pair Dustin Fletcher and Michael Hurley against Collingwood reflected their key-position depth, depth that would make for some tough selection decisions in the coming weeks.

"But the (key-position) players understand that they're part of a group and we'll put the best team out there week after week and the talls understand that they may not play every week but they're a very important part of our team," Hird said.

Key defender Jake Carlisle went off the ground late in the third quarter after landing awkwardly in a marking contest, but Hird said he should be available to play against Greater Western Sydney next round.

Hird said Carlisle had suffered a strain in a foot ligament that should heal in three or four days.

Nick Bowen is a reporter with AFL.com.au. Follow him on Twitter: @AFL_Nick