O'Shea (25) won a bronze medal in the 400m hurdles at the Australian championships in Melbourne in a time of 50.74sec behind Australians Ian Dewhurst (New South Wales) 49.52sec and Tristan Thomas (Tasmania) 50.13sec.
O'Shea ran 52.02sec to qualify and 51.19sec in the semifinal.
He turned the tables on the Waikato-Bay of Plenty athletes who had beaten him all season - Cameron French was fourth in 50.86sec and Michael Cochrane sixth in 51.81sec.
''That was small consolation,'' O'Shea said.
''Cam won the New Zealand champs and Mike broke the New Zealand record.
''But at the end of the day, I would rather have finished last and run the qualifying time. I never planned on this. It will be back to the drawing board for me to see what options are there.''
There has been pressure on O'Shea in every race since he has attempted to reach the qualifying time from the middle of January.
''I have tried not to stress and over-analyse but I was very aware that there was a lot riding on my shoulders every time I stepped on to the track,'' he said.
He ran his best time of 50.16sec when he broke a 41-year-old Otago senior men's record at the Australian championships last year.
His best time is just 0.46sec short of the qualifying standard.
''That's been the story of my season,'' O'Shea said.
''I've run good races and haven't had the weather on my side or I've the weather on my side and I've hit a hurdle and things haven't gone quite right.
''I've yet to put a race together where everything goes right for me.
''My flat 400m times this season show that I'm capable of running the time.''
O'Shea arrived back in Dunedin late on Monday night and has not had time to discuss the prospects with his coach Brent Ward.
''At the moment I don't have any plans,'' he said.
''There is talk about Cam and myself being integral parts of a 4 x 400m relay.''
They would need to run a 400m flat time of 46.80sec for the team to qualify for Glasgow.
Former Otago athlete Andrew Whyte (46.25sec) and Aucklander Tama Toki (46.77sec) have run the required times.
Two other runners have to reach the qualifying time of 46.80sec to get the team to Glasgow.
O'Shea and French have both run 47.40sec this season and are ranked third and fourth.
The deadline to make the team in either the 4 x 400m relay or the hurdles is May 25.
Other Otago athletes also reached the podium in Melbourne.
Marshall Hall was third in the discus with 54.32m, Holly Robinson first in the para ambulant F46 javelin (34.13m) and Rory McSweeney second in the F44 javelin (45.35m).
Tori Peeters was seventh in the javelin (49.04m) and Jerram Huston ninth in shot put (14.84m).
Nneka Okpala broke Tania Dixon's (Otago) 17-year New Zealand women's national record of 13.48m with her silver medal-winning 13.55m in the triple jump.
