The Finn completed only 10 laps in the Alfa Romeo C42, the least of any driver on the day, as his team struggled with reliability issues.
Barcelona was the first venue to showcase these new challengers, with the ten teams taking to the track for a three-day testing session.
Alfa Romeo became the final team to reveal their challenger's livery for the season, which they described to be a subtle nod to the past.
Watford got off to a fast start with a series of corners in the first two minutes, but it was Ronaldo who got the first shot away.
The middle order of the Indian team played a crucial part in the team's victory, with Shreyas Iyer leading the charge.
Horner also believes that the former race director received insufficient support, and he wished him the best of luck.
The Brit set the pace for McLaren on the first day of testing at the Circuit de Barcelona-Catalunya, finishing fourth overall.
Russell's morning time was still good enough for second place at the finish, while Perez and Verstappen finished third and fourth.
Harris has three ATP Challenger singles and two Challenger doubles trophies, as well as 13 ITF singles and four ITF doubles titles.
Alcaraz reached the No. 22 spot in the world as a junior and won two titles on the International Tennis Federation (ITF) junior circuit.