Max Verstappen returns to the scene of his maiden Formula One victory chasing his fourth consecutive Spanish success this weekend with his Red Bull team hoping a rule change will end McLaren's supremacy.
The four-time world champion triumphed on his Red Bull debut as a teenager at the Circuit de Catalunya in the 2016 Spanish Grand Prix and will hope another win, his fifth in Spain, will propel him into the thick of the title race.
The 27-year-old Dutchman is 25 points adrift of championship leader Oscar Piastri and 22 behind his McLaren team-mate Lando Norris, who their rivals believe could be hampered by the introduction of strict front wing flexibility tests.
"It's a significant change," said Red Bull boss Christian Horner of the requirement for much stiffer front wings.
"There will be some effect and, of course, the teams have anticipated this so it may well be neutral. Or it may affect tire degradation. It doesn't make life easier!"
McLaren's excellent aerodynamic car, designed to enable their drivers to manage tire-wear and deliver fast times, may be more hit by the tightening up of the rule than others.
"But we don't know how it will affect them," added Horner.
Formula One announced the clampdown on so-called "flexi wings" in January.
The change left the teams with time to prepare and may have a dramatic effect on performance and the outcome of the season.
"With 16 races left, there is a long way to go," said Mercedes team boss Toto Wolff.
"The team is pushing to find performance and this weekend's updated front wing technical directive will provide another level of intrigue."
After a dismal pointless weekend in Monte Carlo, Wolff expects an upturn from his "silver arrows" drivers George Russell and Kimi Antonelli.
Ferrari's Fred Vasseur said: "This can be a game-changer for everybody because we don't know the impact on every team."
McLaren have won six out of the eight races this year and sit 172 points clear of Mercedes in the teams' title race, but know the "mixed" Spanish track, where there are as many slow corners as fast, may be a challenge for their car.
But after strong results everywhere this season, except on the high-speed tracks at Suzuka and Imola where Verstappen won for Red Bull, they will be under scrutiny and pressure.
As will Ferrari after an inconsistent and mostly disappointing start to the season as seven-time champion Lewis Hamilton continues to seek his first win with the team at a venue where he has won six times – a record he shares with Michael Schumacher.
Two Spanish drivers will take part this weekend: Fernando Alonso of Aston Martin, due to start his 410th race at the age of 43, and Carlos Sainz, 30, of Williams, set for his 215th race.
Their presence has maintained the sport's relatively-new modern popularity and the growth of big crowds at Spanish Grands Prix.
Furthermore, Sainz, born in Madrid, is an ambassador for a future race near the capital, from 2027, while Alonso fulfills a similar role for the Catalan track, which runs out of contract next year – a conflict that enables them to reflect Spain's most classic and enduring sporting rivalry.
