Laura Muir kicked off her season in typically impressive style with third place in the 1500 metres at the Prefontaine Classic in Oregon, despite battling a severe bout of hayfever.

The 24-year-old, starting the defence of her Diamond League title, was in the shake-up headed into the last lap but saw Olympic champion Faith Kipyegon pull away before losing out on second in a photo finish with her fellow Kenyan Hellen Obiri.

“With the pacemaker changing at the last minute, there was a tactical shift,” said Muir’s coach Andy Young. “But the hayfever was tough. She’s been struggling all week with it. But she has been hammering great times in training.”

Fellow Scot Andy Butchart was eighth in a top-class 5,000 metres in the second-quickest time of his career but he was no match for Mo Farah who delivered a blistering sprint to hold off Ethiopian teen Yomif Kejelcha to win in 13:00.70.

It was a message to my rivals, signalled the four-time Olympic champion, who is preparing to defend his world title in London this summer before retiring from the track.

“There were a lot of people doubting me, saying ‘Mo’s getting old,’” said 34-year-old Farah. “And there was a lot of talk, a lot of good youngsters coming through, a lot of talk and a lot of saying ‘Oh, Mo’s there to be taken down.’ And a lot of stuff from so many guys. It was just better to let your running do the talking and that’s what I’m good at.”

Lynsey Sharp was eighth in the 800 metres in 2:01:23 with South African Caster Semenya matching her 1-2 with Kenya’s Margaret Wambui from last summer’s Olympic final in Rio. While Chris O’Hare insisted the conditions held him in check as he took second in the invitational mile in an outdoor personal best of 3:53.34, good enough for third on the all-time Scottish list. “I’m disappointed not to come away with the win,” he said. “Allergies got the best of my breathing.”

His domestic rival and Edinburgh club-mate Jake Wightman won the 1,500 metres at the IFAM meeting in Oordegem in 3:35.93, seven-hundredths of a second inside the world championships qualifying standard. While Guy Learmonth opened his campaign with second place behind Markhim Lonsdale in the 800 metres at the BMC Grand Prix at Sports City in 1:48.22. “Things are going good,” said Learmonth, who will now head for Bydgoszcz on Friday. “It’s just getting the legs moving properly now.”

Marc Austin, meanwhile, gained another boost to his growing reputation with fourth place at the ITU World Cup in Madrid.

The 23-year-old from Glasgow was among the leaders at the start of the run leg but ended up 69 seconds behind race winner Ryan Sessions of New Zealand in 1:54:09.

“I’m looking forward to World Series Leeds next,” Austin said. “I really want to start pushing for podiums.” Stirling-based training partner Doug Roberts came 29th.

Meanwhile, David McNamee extended his winning streak with victory at the Challenge Salou triathlon.