Veteran allrounder Shane Watson admits he's only got himself to blame after being dropped for Wednesday's 275-run mauling of Afghanistan at the WACA Ground.

Watson was forced to make way for the returning James Faulkner, and he faces a fight to break back into the squad for Sunday's clash with Sri Lanka at the SCG.

The 33-year-old has averaged just 22.3 from his past 11 ODI innings, and his form in the Test arena has also been patchy.

With Faulkner and Mitch Marsh now favoured at Australia's premier ODI allrounders, Watson faces a fight to win back his World Cup spot.

But he's not giving up hope.

"I believe in myself and my own abilities. If an opportunity comes along, I'll be ready to go," Watson said before he flew from Perth to Sydney on Thursday.

"I know I haven't scored enough runs, so I've only got myself to blame. That's the way it goes.

"There are things I've made adjustments on even before I got dropped to try to improve and give myself a better chance to score runs and perform.

"I'm always trying to get better and learn, so that's all I can do."

Watson enters the WACA Ground for the anthems // cricket.com.au

National selector Rod Marsh pointed to Watson's run drought as the reason behind him falling in the pecking order behind Faulkner and Marsh.

"Faulkner's in for Shane Watson, which is a big decision but it’s one we thought we had to make," Marsh said before Wednesday match against Afghanistan.

"Unfortunately he's been getting starts but he hasn’t been going on with it, and we had to fit James in and someone had to go.

"I'm not saying it was a choice between any players, but it just happened to be it was Shane’s time to go for this particular match."

Watson was dismissed for a first-ball duck in Australia's opening match of the World Cup against England and scored 23 against New Zealand on Saturday.

The right-hander registered scores of 16, 41, 22 and 34 in the ODIs that preceded the tournament having missed three matches of the Carlton Mid ODI Tri-Series with a hamstring injury.

Watson has a formidable record in ODI cricket; he averages 40.15 from 182 matches with nine centuries and 31 fifties, but hasn't passed three figures since he scored 102 against India in October 2013.

He also hasn't taken a wicket in the past six ODIs in which he's bowled and hasn't taken more than two wickets in an innings in 18 months.

Wattson's wicket-taking has been sparse // Getty Images

Marsh said Watson could yet play an important role later in the tournament.

"It doesn’t mean anything going forward, except that he’s not in the XI at the moment," Marsh said.

"If things change then there’s no reason why he won’t be back in the XI.

"He’s a fine, fine player ... it was a tough decision – no-one likes to leave out anyone. Hopefully he’ll find himself back in the team at some stage.

"He might have to rely on someone else’s lack of form or an injury to get back in (the side), but it’s a good situation to be in really when you’ve got both Watson and George Bailey out of the side – two extremely well-credentialed one-day players."

Marsh looked proppy during his three-over spell against Afghanistan, appearing to grimace in pain during his third over. But Australia skipper Michael Clarke said it was nothing more than an issue with Marsh's shoes rather than a flare-up of his troublesome hamstrings.

"It was something to do with his boot," Clarke said.

"I asked him if he was all right and he said, 'I'm completely fine'."

"I thought Watto handled (his axing) really well," Clarke added.

"It's obviously a tough decision for the selectors."

Watson scored 23 against New Zealand // Getty Images

World Cup winner Shane Warne said Watson's run of mid-range scores had caught up with him, but said the allrounder's tournament was far from over.

"I suppose they've just said 'you know what, we're sort of sick and tired of Shane Watson not making runs'", Warne told Wide World of Sports.

"I still think he could play a part in this World Cup, because I look down that side at the moment and you've sort of got three or four number sevens batting at 5, 6, 7 and 8.

"There's a lot relying on that top order so Shane Watson could still have a lot to say in this tournament yet.

"He's missed out today, they've given him a bit of a clip just to say 'we've worn thin about your (lack of) runs. You've needed to make some runs and you haven't been able to do that.'"

Smith scored 95 at No.3 against Afghanistan // Getty Images

Former World Cup captain Mark Taylor agreed that Watson, when in form, deserves selection in Australia's best XI. But he warned that Steve Smith's assured 95 at No.3 would make it especially difficult for the allrounder to regain his spot in the side.

"I think Shane Watson, at his very best, does bat at No.3 for Australia," Taylor said.

"If Australia play well, it's going to be hard for Watson to get back in, especially if Smith or Clarke make runs.

"This could be Australia's side for the rest of the World Cup, if they play well."