Siddle joined Notts on a two-year deal ahead of last season, but did not play last summer because of a back injury.
And the 32-year-old has now withdrawn from playing in the 2017 county season.
Pattinson, 26, has taken 70 wickets in 17 Test matches for Australia, with his last appearance coming against New Zealand in February 2016.
He took his first five-wicket haul in first-class cricket since December 2015 in Victoria's Sheffield Shield win over Western Australia on Saturday, a result which secured the Bushrangers a place in the final.
"I feel for Peter in particular because he's had absolutely no luck in recent years when it comes to injuries," Nottinghamshire director of cricket Mick Newell said.
"We certainly didn't imagine, when we signed him on a two-year contract for 2016 and 2017, that he wouldn't play a single game for us during that time."
Nottinghamshire were relegated from Division One of the County Championship last season, having won just one of their 16 games.
Nottinghamshire have targeted Australia paceman James Pattinson to replace injured Peter Siddle as their overseas player, BBC Radio Nottingham reports.