Red Bull has a new partnership with Honda this year after more than a decade with Renault, whose engines powered them to four successive driver and constructor title doubles between 2010-13. Second chances used to be rare in F1, but comebacks appear to be in vogue.
He did concede, however, that while he didn't expect Honda to be able to match Ferrari and Mercedes' power outputs in the first few races of the season, his aim for the year was to finish up - as he did in 2018 - as a multiple race victor. If the answer to that is "no", you have to wonder why Toro Rosso has hired him again, given that its very existence is largely to develop talent for the A-team.
The 21-year-old was forced by governing body the FIA to attend a race of the all-electric Formula E series and observe the stewards.
Horner was sure the Honda partnership would be very different.
His maturity was on display during the second half of the 2018 season, when he was the second highest point scorer on the grid, only behind Lewis Hamilton. "I will always try to get the best out of myself and hopefully that is enough".
One of the main areas that Honda will need to improve in 2019 is its reliability, with Red Bull eager to avoid a repeat of the spate of engine penalties that sister team Toro Rosso endured last season.
"We would prefer constant development, even if it means we would have to put up with one or two penalties", he said. "We're not expecting to go to 100% clean sheet of paper but what we are extremely hopeful of is that the performance will be a step from where we've been in the last few years".
Horner said it would be "very interesting" to see how Charles Leclerc gets on in his first season at Ferrari, following his promotion from Sauber.
And he said Mercedes could stumble under pressure if their dominance was not as great as in the past. They are making good progress.
But Horner said he believed it would make no difference to the on-track action, although he said it might lead to some variability early in the season because "some people will have got it right and some people will not". I think it's there now from both sides - the team and the engine supplier.
Horner described this as "quite a naive approach".
"It's vitally important any restructure is done on a fair and equitable basis". We'll have to wait and see, me too.