Jadeja was replaced by Yuzvendra Chahal as a concussion substitute.
Chahal was originally not named in the playing XI but Jadeja was hit on the helmet during the last over of India’s innings, and as BCCI medical team assessed him, he was replaced by the wrist-spinner as a concussion substitute.
WATCH - Irked Langer gets into argument with Boon after Chahal replaces Jadeja
As it turned out, Chahal claimed 3 wickets by conceding 25 runs in his four overs to help the visitors register a convincing 11-run victory in the T20I series opener.
"He got hit on the helmet in the last over (off Mitchell Starc) and when he came back to the dressing room, he was asked by the physio (Nitin Patel) how he felt. He (Jadeja) said that he was feeling a little dizzy," Samson told mediapersons during the post-match virtual media conference.
"He is under observation as per team doctor's (Dr Abhijit Salvi) advice."
Samson, however, couldn't provide any update on how Jadeja's hamstring is after he picked up a niggle and needed heavy strapping during the 19th over bowled by Josh Hazlewood.
"I don't know how Jaddu bhai is feeling as the physio is taking care of that."
Samson was full of praise of Chahal, who got the prized scalps of Aaron Finch, Moises Henriques and Matthew Wade during Australia’s innings.
"That is the standard that has been set by this team. The quality of players is so high that anytime you ask, they are ready. Chahal grabbed his chance and it was a great lesson for everyone that they need to be ready all the time."
Sanju Samson hasn’t got much success in the five T20Is he played for India so far. However, the youngster is not taking any additional pressure on himself.
"A few years back I would have said yes (pressure factor) to that question. But now I have played a few matches for India and have been around good people, who have helped keep a positive mindset.
"The idea is to keep it simple and focus is to win every game for India," Samson said.
(With PTI inputs)