Lefau, who was "deeply embarrassed" when caught by police last month, is one of four Tigers changes for the clash with Gold Coast at the MCG on Saturday.
The New Zealand-born key forward returns alongside experienced pair Nick Vlastuin and Dion Prestia, as well as Tom Brown, with Rhyan Mansell (wrist) and Jonty Faull (suspended) unavailable.
The red-hot Suns have been bolstered by the return of Bailey Humphrey and Charlie Ballard as they chase a third-straight win to start the season.
St Kilda, who are winless from two outings, have regained ruckman Rowan Marshall from concussion for their meeting with GWS at Engie Stadium on Saturday.
Jack Macrae (knee) is out, but sore pair Mattaes Phillipou (thigh) and Liam Ryan (shoulder) both trained on Thursday and were named for the Saints.
The Giants are unchanged despite being thrashed by the Western Bulldogs last week, while Melbourne also opted against changes for their clash with Fremantle at Optus Stadium on Saturday night.
The Dockers suffered a huge blow when Young was ruled out with a "low-grade" hamstring injury, which is set to sideline him for up to a fortnight.
Scerri is his replacement, deemed ready for his AFL debut just weeks after earning a spot on the list through the pre-season supplemental selection period.
"It's been a crazy two months. I really haven't sat down and taken all in," the 19-year-old said.
"Who would have thought only two weeks ago or even a bit more, I signed with Freo and now I'm debuting round two.
"Things can happen really quickly and you just gotta get up to it."
Adelaide have regained match-winner Izak Rankine, who will play his first game of 2026 against the Western Bulldogs on Friday night, after serving a four-match ban for a homophobic slur.
The Bulldogs regained Jordan Croft and left out Will Lewis as they pursue a third straight win to start the year.
Essendon named exciting youngster Isaac Kako in the extended squad to face Port Adelaide on Sunday after he overcame a hamstring strain.
Jade Gresham was also named, while Port Adelaide included Jordon Sweet, Will Brodie and Jack Lukosius among five possible inclusions.
West Coast dropped 2018 premiership defender Tom Cole, with co-captain Liam Baker back from suspension and Tim Kelly named on the bench for Sunday's clash with North Melbourne.
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