Su'a, 21, had already agreed to join the Redcliffe-based club from the start of next year on a two-year deal.
The agreement on a player exchange has enabled him to do so sooner after he played 30 games for the Knights in 2023 and 2024, but none in the current season.
Teague, also 21, was off-contract at the end of this year with the Dolphins and had not played any NRL in 2025 after lining up in eight matches in his first two seasons at the club. He will bolster the Knights' middle forward rotation.
AAP has been told Su'a will start training with the Dolphins in the coming week. His arrival, and Teague's exit, means the club's top 30 is now set in stone for this year.
The Dolphins have signed former St George Illawarra prop Frank Molo until the end of 2026, and he is close to making his NRL debut for the club after his move in March.
Molo, 30, has played two games for the CQ Capras in the Queensland Cup.
The Dolphins do have salary-cap space and room for new signings or extensions for 2026.
The Dolphins have four key forwards off-contract at the end of this year: Josh Kerr, Felise Kaufusi, Mark Nicholls and Kenny Bromwich.
Two-time Melbourne premiership winner Bromwich, 33, is undecided whether he will play on or retire and join his brother Jesse Bromwich in the carpentry trade.
"Not too sure yet. I am just looking to enjoy this year," Bromwich said.
"I am working with my brother and doing our apprenticeship. I am enjoying that and will definitely be doing that down the track."
Kerr, 29, was outstanding off the bench in the win over Penrith on Thursday night. The giant prop would like to stay and secure a new deal at the club where he played his junior football.
Kaufusi, 32, and Nicholls, 35, are both highly regarded members of the Dolphins' leadership group.
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