Former Test captain Smith had been named to lead Australia for his first full series since the South African ball-tampering saga after Pat Cummins opted to stay home for the birth of his child.
But the veteran batter hurt his right elbow throwing in the field during the Sydney Sixers' washed-out BBL derby against the Sydney Thunder on Friday, only 10 days out from the first match in Galle.
Smith is set for consultations with a specialist this week to determine his return-to-play timeline.
Steve Smith will need to prove to team medicos he is ready to play the first Test. (Mark Evans/AAP PHOTOS)
Thunder opener Warner had been hitting to all corners of the ground when his former Test teammate hurt his elbow throwing from the field.
"Obviously that's a big blow if he potentially misses the Sri Lanka tour but I think he'll be able to get through it," Warner said.
Cricket Australia is similarly hopeful Smith will be available for the Sri Lanka series, but would likely appoint Head as the country's 48th Test captain if the star No.4 does not pull up in time.
Considered a Test captain-in-waiting earlier in his career, Head had been named vice-captain for the Sri Lanka series and famously became South Australia's youngest Sheffield Shield captain at 21.
Warner, himself a former Test vice-captain, had endorsed Head to open the batting on the tour and had no doubt he would capable adding the captaincy to his remit.
"I don't think he'd say much. He'll just make changes when he feels like it, he'll be fine. He's done the job for South Australia for a long time as well," Warner said.Â
"He's got a good head on his shoulders."
Warner predicted Head would be a popular captain amongst the squad, having become well known for his post-victory celebrations in recent years.
Smith's injury has delayed his arrival at a camp at the ICC Academy in Dubai, where the Australian team will prepare for the turning wickets and sticky weather awaiting in Sri Lanka.
David Warner has backed Travis Head to captain the Test side in Sri Lanka if Steve Smith is out. (Dan Himbrechts/AAP PHOTOS)
The majority of the squad flew out to the United Arab Emirates across the weekend, with Smith's flight now delayed until later in the week.
His injury comes as spinner Matthew Kuhnemann hopes to prove his fitness for the two-match series after undergoing surgery on a thumb injury to his non-bowling hand suffered in the BBL.
Kuhnemann's flight out of Australia has also been delayed, but the 28-year-old is expected to resume bowling later this week with the view to joining the squad in Sri Lanka.
Warner nominated Thunder teammate and left arm off-spinner Tom Andrews as an out-of-the-box replacement should Kuhnemann fail to pull up in time.
He was less sold on suggestions 21-year-old allrounder Cooper Connolly could operate as a front-line spinner in Kuhnemann's absence.
"Connolly (would) have to bowl 25 overs ... they could throw someone like Tommy Andrews over there as well," Warner said.
"You've got a good back-up there in Todd Murphy. It is two bowlers (Murphy and Nathan Lyon) bowling the same (offspin) but when you've got quality, you might as well use it."
