Melbourne Stars released Clint McKay from the final year of his contract so he can sign a deal with Sydney Thunder. The Stars have also lost opening bowler Jackson Bird, with the 28-year-old believed set for a move to his former home town of Sydney, with the Sixers.

In Bird's place the Stars are set to sign Ben Hilfenhaus, from Hobart. The Hurricanes could lose two of their most senior bowlers, with left-arm, finger-spinner Xavier Doherty expected to join the Melbourne Renegades.

Stars captain Cameron White is not yet among the most highly sought-after players, with his team declining to offer him a new deal until they decide whether to reappoint coach Greg Shipperd or install a replacement.

Thunder general manager Nick Cummins said there was frenetic competition among Big Bash League teams for players.

"With the salary cap going up by $100,000 per team, so that's $800,000 total, and maybe 80 players coming off contract there's been a real frenzy around the top players," he said on Monday, at the start of the first of two BBL trade periods.

"If you're a good player and performing well it's certainly very hard to sign you without someone else putting in a bid as well. It's very, very competitive, because the depth is not massive."

Cummins said he was rapt to have snared Ben Rohrer, a player whose Twenty20 form saw him play for Australia two years ago, in a one-way trade with the Renegades.

"He's highly respected in NSW ... everyone in NSW is aware of what he can bring, not just with the bat but also off-field," he said of the 33-year-old.

"You've always got to look at the form line and [also] the player. Aiden Blizzard was the same. He didn't have a great year at the Hurricanes the year before but he's a good player."

Cummins said the signing of Rohrer was partly done with an eye to succession, with Mike Hussey not expected to play beyond next season.

"We were very fortunate to get Mike two years ago when no one really wanted to come to the Thunder. We just have to make sure that when he finishes that we don't go all the way back to the start again ... almost Sydney Swans of the late 1980s style of getting all these great players and when they all go, you go back to being a basket case. We have to think about succession, and Ben is part of that, and retaining Gurinder (Sandhu), Usman (Khawaja) and Pat (Cummins) ... having this core of players who are synonymous with the Thunder."

Cummins said the bright international prospects of Sandhu and Cummins, and the resulting cut in their availability for the Thunder, had spurred their interest in signing McKay, although the deal is yet to be formalised.

"We've got concerns about our fast-bowling depth if Pat and Gurinder continue on their trajectory we run the risk of losing them to Australian duties, and we've got to make sure we've got someone in backup," he said.

"With any of these signings you've got to look for blokes who are 'unders', guys who are better than what their stats show. He's a great bowler and he showed that in the games he played for the Stars in the last few games, and bowling the maiden to Andrew Tye [in the semi-final]."

McKay, who has just turned 32, is ranked 19th in the world for one-day bowlers despite being overlooked for Australia for the past 13 months.