Walsh threw 21.50m near his German base of Mannheim, the sixth furthest of any thrower this year. The mark would have earned third at the 2013 world champs.
Walsh should qualify for tonight's final at the Bird's Nest.
He thrives in mental cauldrons, like last year's world indoor championships in Poland when he became the first New Zealand man to earn a medal with bronze.
Fellow Kiwi Jacko Gill has won multiple world junior titles and set world records at every level but, at 20-years-old, is still developing at senior level.
In contrast, Walsh (23) is embracing the camaraderie of his brothers-in-big-throwing-arms in his first full season as a professional.
He has trained with the American trio of former world champion Reese Hoffa, double world indoor champion Ryan Whiting and up-and-comer Jordan Clarke.
"We're all quite good mates, or I like to think we are, but it doesn't matter how well you are getting on and if you're rooming together, you still want to win," Walsh told the Herald on Sunday in Monaco.
"There's a bit of trash-talking. Someone might say 'see how good I'm warming up this morning?' and I might say 'gee, my standing throw's about 16m at the moment — which is good for me — so watch out boys, it's coming'.
Walsh has not struggled for acceleration with his throwing arm, consistently delivering greater than 20.70m this Diamond League season (20.81m for fourth at Eugene, 21.16m for third at New York, 20.86m for fifth at Lausanne, 20.73m for fourth at Monaco).
Willis turned 32 on Anzac Day but has excelled over the past 13 months, securing personal bests in the 1500m, mile (indoors and outdoors), 3000m and 5000m.
Speaking after his Monaco race, he said: "It's my best race time-wise so I must be in some of the best shape of my life. The blessing of this race on calendar for the world championships versus the London Olympics is that there are six weeks to go rather than three. This will also give me a good seeding going into world championships, so the heats won't be stacked with too many good guys. It puts me in the top five or six in contention for medals.
"I've enjoyed a long bout of health without injuries, which has allowed me to put in an Arthur Lydiard-type mileage base this season."
He recently tweeted that after the 2014 season he sought advice from middle distance great Steve Ovett who suggested "Stop thinking so much, Nick. Just race."
Willis has since trained at altitude in Arizona. The 1500m final is scheduled for next Sunday.
Of the other New Zealand men in Beijing, Michael Cochrane raced the 400m hurdles heats last night, Stu Farquhar is throwing the javelin at his fifth consecutive world championships and Quentin Rew is in the 20km and 50km walks.
Other recent close calls
• A women's golf major winner
Lydia Ko was second at the Evian championship in 2013.
• A Tour de France individual stage winner
Jack Bauer came within 50m on the 222km stage 15 of last year's Tour de France before being overtaken by the peloton.
• A Cricket World Cup
New Zealand were beaten by Australia in their inaugural final at Melbourne during March.
