Zurich - Justin Gatlin will take on Noah Lyles in what promises to be another thrilling 100m at Thursday's Diamond League meet in Zurich, the American duo fine-tuning preparations for the world championships in Doha.
Gatlin, at 37, is 15 years older than Lyles (who will only race the 200m at the September 27-October 6 worlds in the Qatari capital) and last time out had to race like a "bat out of hell" to beat him.
The veteran sprinter, the 2004 Olympic 100m gold medallist and current world champion who served a doping ban between 2006-10, is a long-standing fixture on the track, albeit a controversial one, but continues to show his enduring prowess.
Last month in Monaco, Gatlin kept both his nerve and form after an average start to streak through the finish line in 9.91 seconds, just one-hundredth of a second ahead of much-vaunted Lyles.
And Lyles is very much an in-form runner, having posted two very quick times over his favoured 200m, including a 19.50sec in Lausanne that made him the fourth fastest ever sprinter over that distance.
Gatlin has admitted to feeling that this season is "surreal, I can't believe I'm still winning here after more than 20 years".
"It's a hard feeling being the old guy," he told AFP.
Gatlin won world gold in London in 2017 ahead of fellow American Christian Coleman - in the spotlight for missing three drugs tests - and now-retired Jamaican sprint legend Usain Bolt.
Not only is Gatlin plotting to defend his title in Doha, but he is using that as a handy warm-up for a fourth Olympic Games campaign at Tokyo 2020.
"I really try not to set a (retirement) date for myself," Gatlin said at last month's US trials.
A loaded 100m field at the 25,000 sell-out Weltklasse meet at Zurich's Letzigrund stadium also features Jamaican Yohan Blake - the 2011 world 100m champion who set a meeting record of 9.67sec during his last appearance in Zurich in 2012.
Also lining up will be British duo Adam Gemili and Zharnel Hughes, American Michael Rodgers and South Africa's Commonwealth champion Akani Simbine.
The women's 200m also has a stellar line-up, with Dina Asher-Smith back on the circuit after winning the 100m and 200m silver at last weekend's British championships, the former in a champs record of 10.96sec.
She faces Jamaican Elaine Thompson, the reigning Olympic double sprint champion, and current world champion Dafne Schippers of the Netherlands.
The tussle of the evening, however, could come in the women's 1 500m, in which Ethiopia's Genzebe Dibaba faces off with Sifan Hassan, the Ethiopian-born Dutch runner.
Dibaba is the world record holder in the 1500m and currently holds six additional indoor and outdoor world leading times.
Hassan, in turn, ran the fastest mile of all time in Monaco last month.
Men: 100m, 800m, 5000m, 400m hurdles, pole vault, high jump, long jump, javelin
Women: 200m, 400m, 1500m, 400m hurdles, 3000m steeplechase, triple jump, javelin, shot put