MEXICO CITY (Reuters) - Williams, sponsored by drinks company Martini, say age considerations will not be key to deciding who races for them next season after their 18-year-old driver Lance Stroll had to wear team kit without alcohol branding in Japan this month.

The newly announced Williams Martini Racing driver for the 2017 season Lance Stroll attends a media conference at their base in Wantage, Britain November 3, 2016. REUTERS/Eddie Keogh

It has been widely assumed in the Formula One paddock that the former champions need someone over 25 for marketing purposes given that Canadian rookie Stroll is set to remain.

Stroll, whose current Brazilian team mate Felipe Massa is 36, had to go without alcoholic branding on his kit at the Japanese Grand Prix because he is below the legal drinking age.

If both drivers were underage, that could cause a sponsorship headache.

However team technical head Paddy Lowe told reporters at last weekend’s U.S. Grand Prix that it was not the key consideration.

“What’s most important for the team is to pick a driver lineup that will give us the best performance and most exciting racing potential,” he said.

“There are some issues around advertising and Martini but if it came to it, I’m sure Martini would understand the importance -- if that’s what we were to choose -- to have the best lineup for racing rather than for advertising.

“We will cross that bridge if we need to. Age is not a factor in our primary objective which is to pick the best lineup.”

Williams have tested Poland’s Robert Kubica and Britain’s Paul di Resta, 32 and 31 respectively, as possible replacements for Massa, who also remains in the frame but is expected to depart.

Kubica has been out of the sport since he partially severed his right forearm during a 2011 rally crash but has tested a 2014 car without problems. Former Force India driver Di Resta is the official reserve.

MULTIPLE OPTIONS

Others are also under consideration, including Sauber’s 23-year-old Pascal Wehrlein.

The German is backed by Mercedes, who provide Williams’ power units and are run by former Williams shareholder and director Toto Wolff. Lowe also worked with him at Mercedes before joining Williams.

The youngster looks sure to lose his place at the Swiss team to Formula Two champion Charles Leclerc, who is a member of the Ferrari driver academy. Sauber use engines provided by the Italian team.

Lowe said Wehrlein and others remained in contention and Williams were under no pressure to make any announcement, even if Massa would like a decision before his home grand prix in Sao Paulo next month.

The Brazilian said farewell to fans there last year, only to return when Valtteri Bottas left Williams suddenly for Mercedes after 2016 champion Nico Rosberg retired.

Wolff said Williams appeared to be Wehrlein’s only option but there was only so much Mercedes could do.

“At a certain stage of a driver’s career there comes the moment where it’s not about paying any more but standing on your own feet,” added the Austrian.