Warner did not take the field during Sri Lanka's chase after suffering a groin complaint during his 157-ball, three-and-a half hour effort that finally ended on the last ball of the innings when bowled by Dhammika Prasad (2-51).
He appeared in doubt for Tuesday's second clash in what must be a major concern for Clarke.
But the skipper was more worried about his bowling attack after Sri Lanka ensured plenty of anxious moments.
"At 6-144 I was thinking you can't lose the game from that position,'' Clarke said.
"A win is a win. But we have a lot of work to do with our power play and death bowling.
"It hasn't been good enough all series. It continues to let us down.
"We are the No.1 one-day team and we have to be better than that.
"Hopefully that (scare) allows us to understand that we have to be better than that.''
Remarkably Warner was considered a chance to be dropped on Sunday in a team reshuffle for Clarke's return from injury.
Warner would have been nervous after a modest series return of 195 at 24.37.
Indeed the NSW left-hander had never really shone on the ODI stage, averaging just 22.5 in 18 games with three 50s before the Gabba clash.
However, Peter Forrest - the only other Australian batsman to hit a ton this series - was rested.
But Forrest took the field during the Sri Lankan innings so Warner could rest after becoming the seventh Australian to break through the 150-run barrier in ODIs.
Asked if he would play on Tuesday, Warner said: "Hopefully.''
Sri Lankan skipper Mahela Jayawardene took heart from the spirited display.
"I am quite happy with the effort from the boys,'' he said.
"We didn't play a perfect game today. And 320 was always going to be a tough score - especially with rain.
"But the boys, at the end, showed some real character and kept fighting which is something you want to cultivate in a team.''
Matthew Wade (64) put on a 136-run opening stand with Warner before being spectacularly caught by Rangana Herath on the long-on boundary.
Two brief rain delays disrupted Australia's innings but falling wickets worried the Sri Lankans during the early part of their dig.
Brett Lee (3-59) and David Hussey (4-43) helped rip through the top order before the tourists hit back - literally - through Kulasekara who had two lives in a 104-run, seventh-wicket stand with Tharanga.
- AAP