A minor interruption to Zousain's autumn build-up has cast doubt over whether the colt will make his return in the Group One Lightning Stakes or wait another week.

Trainer Chris Waller was at Flemington on Friday morning to watch three-year-old colt Lean Mean Machine tune up for his return in Saturday's week's Lightning with a comfortable jump-out on the straight course.

Zousain has also been on a path towards resuming in the Lightning ahead of the Newmaket Handicap but had a slight temperature late last week.

Waller said Zousain had scoped clear of any mucus on Thursday and a blood test also came back clear.

"He had a gallop this morning and he worked well and he will trial on Monday (at Rosehill)," Waller said.

"It means the Lightning is doubtful but we won't say no yet.

"If he didn't run in that race there's a race at Caulfield a week later over 1200 metres for three-year-olds (Zeditave Stakes), and he will definitely run in the Newmarket."

The Group One Newmarket (1200m) is on March 9 and Zousain is equal favourite at $8 in an early market.

"There's certainly no doubt about the Newmarket, he'll run there," Waller said.

Zousain has been placed three times at Group One level, including his second to Sunlight in the Coolmore Stud Stakes in the spring at Flemington in which Lean Mean Machine was third.