Now with injuries, international commitments and players moving elsewhere, the Sixers have limped to their fourth consecutive Big Bash League loss and have gone from being champions to wooden spoon candidates heading into their clash against Sydney Thunder at ANZ Stadium on Sunday night.

All-rounder Steve Smith pointed to a bowling arsenal of Mitchell Starc, Pat Cummins and Josh Hazlewood, which helped lead the Sixers to an inaugural Champions League title in October.

"The three fast bowlers were too much for the others teams and we've lost all of them," Smith said. "The team we've got right now isn't quite as balanced. It's a completely different team to the one we had [in South Africa]. We've been lacking a bit of depth in the batting and bowling department."

While Brett Lee returned for a second season with the Sixers after playing for Kolkata Knight Riders in the Champions League, the Sixers have not had the services of Hazlewood or Starc through injury and international commitments respectively.

Cummins, who is out injured, had signed with Perth Scorchers for the BBL anyway, forcing the Sixers to rely on relative unknowns including Luke Feldman and Josh Lalor to spearhead their attack.

Their overall depth has been tested too with Hazlewood, Starc, top-order batsman Nic Maddinson and opener David Warner all unavailable for their seven-wicket loss against Hobart Hurricanes at the SCG on Wednesday night.

The return of England international Michael Lumb, who scored 35, provided some stability at the top of the order, with the team blooding rookie batsmen Kurtis Patterson and Daniel Hughes.

"[Lumb] is a very good inclusion and had a very good year for us last year," Smith said. "Shame he wasn't here at the start of the tournament but he is here now so hopefully he can play some good cricket."

The loser of the Sydney derby is in real danger of finishing last.

While the Thunder are yet to taste victory from their opening four games, the Sixers remain a slight chance of an unlikely finals spot, provided they win their remaining three games and other results are favourable.

"We've got to win every game and try and win well," Smith said. "There's not too much else we can do. It was probably one of our better performances [on Wednesday night]. If we have Maddinson back it'll help create a big enough score to be a contender."

The Thunder play the Heat, who are chasing just their second win, at ANZ Stadium on Friday night.