Onions had only recently returned from a back injury that sidelined him for six weeks and is facing a similar spell out of action due to an injury on his left internal oblique muscle.
The 31-year-old suffered the problem while bowling his opening over in the Royal London One-Day Cup match against Nottinghamshire earlier this week and scans have revealed his campaign is almost certainly over, with Durham’s final game taking place on September 23.
He said: “I was obviously devastated when I received the results of the scan as the next six weeks of the season are hugely important for the team”
“Although I don’t think I can play for the rest of the season, I’ll be doing everything I can to try to get fit and help the lads out during those final few games”
Onions, who has played nine Tests and four one-day internationals for England, was the leading wicket-taker in last season’s LV= County Championship to lift Durham to their third title in six years but injuries have seen him struggle in 2014, with only 12 wickets at an average of 42.
Meanwhile, Durham also announced off-spinner Gareth Breese would end his 11-year association with the club at the end of the season. Breese, who joined the county in 2004, said: “It’s been a very enjoyable time for me. Over the past 11 years, I’ve grown as a player, coach and a person and most importantly formed some great friendships on and off the field.
“The highlights have been the successes we’ve had, not necessarily personal, but just winning trophies as part of a team.”
On the pitch, a fine 84 by Calum MacLeod and an attacking 83 from John Hastings helped Durham stage an impressive fightback against Lancashire to reach 329-8 at stumps on the first day at Old Trafford.
Durham looked in some trouble as they slipped to 82-5 but MacLeod and Hastings joined forces in a 145-run stand for the seventh wickets to help turn the LV= County Championship Division One clash around.
Neither player was able to stick around until the close as both were dismissed in the final 10 overs of the day, but by then Ben Stokes had arrived from the Oval after being released from England duty.
The all-rounder will resume on 24 not out today.
Adam Rossington and David Willey helped Northamptonshire celebrate one of their better days of this season’s LV= County Championship Division One as they seized the initiative against Nottinghamshire.
Rossington scored 103, his maiden championship hundred, as his side posted 260 all out before Willey picked up three crucial top-order wickets to leave Nottinghamshire’s reply in disarray on 38-4 at Wantage Road.
Ian Westwood hit his first century for two years to lead Warwickshire to 334-9 on the opening day with Somerset at Taunton.
The opener made the most of being dropped on 24 to score 129 after his side had lost the toss on a green pitch.
Rikki Clarke contributed 42 to a sixth-wicket stand of 67, while Richard Jones made 35.