Michael McKillop finished fourth in the final of the T38 World Para Athletics Championships 1500m in Dubai.
McKillop's time of 4:09.27 would have been a new championship record in his usual T37 category but in a combined field with T38 athletes it was no match for Canadian Nate Riech, who scorched home in 4:02.04.
Abdelkrim Krai of Algeria was second in 4:04.70 with Australia's Deon Kenzie third in 4:08.49.
Fourth was enough to seal McKillop's place at next year's Tokyo Paralympics however.
First-time finalist David Leavy finished ninth in 4:23.86, a personal best.
McKillop had previously won nine world gold medals (five in 800m and four at 1500m) and four golds across three Olympic games.
The 29-year-old Ballymena native hadn't had a major race since winning the 800m and 1500m titles in London in 2017 as he battled a long-standing groin injury that required surgery.
"Before I came out here I prepared as best I can but I knew that I wouldn't be able to go with the pace from a long distance out," said McKillop.
"I’ve just had eight months in my legs, that’s it. So, if I can do that in another ight months, another year or just below a year on top of this it will get me back in the medals and hopefully back on top of the podium but, again, tonight wasn’t my night, that’s sport for ya, the better people beat me."
Mary Fitzgerald competed for Ireland for the first time at a major championship and came away with a a seventh-place finish in the F40 Shot Put with a throw of 6.87m.
The 20 year old Kilkenny native she finished in just 14cm shy of her personal best mark of 7.01m.
