Jimenez, who won the Open de Espana in 2014 at the age of 50 years and 133 days, has played just three European Tour events in 2017 and spends most of his time playing on the seniors circuit.
But the 53-year-old Spaniard rolled back the years with seven birdies and a solitary bogey at Crans-sur-Sierre to card an opening six-under-par 64 and share the lead with England’s Tyrrell Hatton and 2016 runner-up Scott Hend.
“Anything can happen,” Jimenez replied when asked about his prospects of winning on Sunday. “I’m playing good and feeling good.
“When you hit it good nothing is difficult. I played well, especially my irons to the flag were very good.
“I always enjoy coming here. It’s an amazing place and my 28th time coming here. I only missed one year because it clashed with the Senior British Open [in 2015].”
Hatton has not made a halfway cut since the BMW PGA Championship in May, but holed his second shot to the 12th – his third hole of the day – for an eagle and added five birdies and a single bogey.
“It was a difficult summer so very happy with today’s round and hopefully I can post a few more good numbers this week,” said the 25-year-old, who has slipped from a career-high of 14th in the world rankings to 30th.
“I went through a really good run with the putter but since Austin (the WGC-Dell Match Play in March) I had a little hiccup with the one that worked really well – I punished it – and haven’t found one that works.
“I had it re-shafted but it wasn’t the same, although it did have a few extra battle scars on the bottom of it.”
Scotland’s Duncan Stewart and David Drysdale were in a six-strong group on five under, with former No 1 Luke Donald two under and defending champion Alex Noren on level par.
Stewart is currently 137th on the Race to Dubai and needs some good results to move into the top 100 and keep his card for next season.
“It’s been a long time since I had a bogey-free round and a long time since I got off to a good start in a tournament as well,” the Challenge Tour graduate Stewart said. “I did a lot of work with my coach the last two days. I think I put him through his paces a little bit and thankfully it’s paying off. Being out first and taking advantage of the good greens was good.
“It’s my first time up here. Somebody said this course might suit my game, it’s about plotting your round and not bombing it so it was nice to come here and see that it suits my eye.”
Lee Westwood carded a one-over-par 71 on his 500th European Tour start, while Ryder Cup captain Thomas Bjorn was forced to withdraw after 15 holes due to an ongoing foot injury.