Test aspirant Peter Siddle struck late on day three of Victoria's Sheffield Shield opener against Tasmania to help put the Bushrangers in a commanding position with a day to play at the MCG.

A day out from the naming of Australia's squad for the first Test, Siddle was largely on light duties as his fast-bowling rival Jackson Bird further bolstered his hopes of Test selection. Bird took three second-innings wickets as Victoria searched for quick runs before declaring late on day three, setting Tasmania 365 to win. But Siddle, Chris Tremain and Scott Boland were unleashed and delivered fearsome late spells with the pink ball in the last 45 minutes of play, with Tremain removing Ben Dunk for six before Siddle (1-4 off four overs) trapped Beau Webster LBW for a duck, and Boland dismissed Alex Doolan for two, leaving the Tigers on the brink at 3-19 with Caleb Jewell on 10 and nightwatchman Andrew Fekete yet to score.

Earlier Siddle bowled just three of the 54.3 overs sent down by Victoria either side of tea on Thursday as they bowled Tasmania out for 255 to take a 160-run lead into their second innings. The Bushrangers said that there was nothing wrong with Siddle and that he was merely being managed in what is his return to first-class cricket after eight months out with ankle and back issues.

All-rounder Daniel Christian said Victoria had tried to apportion Siddle's overs strategically.

"We held him back a little bit [earlier in the day] to be able to bowl him more tonight and then again tomorrow," Christian said.

"It worked out really well and everyone else picked up the slack."

Play began an hour early on Thursday after rain interrupted play on day two. Siddle went wicketless in his three overs on day three to finish with tidy figures of 1-18 from 13 overs. The damage was instead done by Christian, who justified his selection ahead of Glenn Maxwell by taking three wickets on Thursday to finish with 4-35. George Bailey top-scored for Tasmania with 64, while Cameron Boyce finished unbeaten on 56 from 53 balls, including taking 20 from one Jon Holland over.

The hosts chose not to enforce the follow-on and extended their lead to 253 at dinner as Marcus Harris continued an excellent first Shield appearance for his new state, top-scoring again with 77 to complement his first innings century. Bird backed up his 30 overs in the first innings to send down 13 overs on Thursday, finishing with 3-59 to make it six wickets for the match. Spinner Webster chimed in with 3-25 before the Bushrangers declared at 9-204. Siddle and Bird shape as the contenders for the third fast bowling spot behind Mitchell Starc and Josh Hazlewood for the first Test against South Africa starting next Thursday in Perth.

Christian was dismissed twice by Bird during the match but gave the nod to Victorian teammate Siddle.

​"I'll be a bit biased towards Sids...he's just a class above I think, should probably be in the Australian team all the time," Christian said.