Wales are sweating on the fitness of Gareth Bale ahead of the showpiece friendly against Spain after the Real Madrid forward missed training on Monday.
Ryan Giggs' squad took part in a session in Cardiff, but Bale sat out having limped out of Real's 1-0 defeat to Alaves on Saturday with a groin problem.
Bale is having the injury assessed and Giggs must wait to see if he can play on Wednesday, in the first Wales match at the Principality Stadium for more than seven years.
Either way, Bale will be presented with a 'Golden Boot' award ahead of kick-off against Spain after moving to 30 goals for his country to top the all-time scoring list ahead of Ian Rush. Wales then travel to Dublin for a Nations League game against Ireland on Tuesday October 16.
Giggs said Wales haven't been asked to tailor Bale's involvement by Real but they won't take risks.
'Sometimes it's not easy, especially for the likes of Gareth, they're in the middle of the Champions League, so there's a midweek game, and at Real Madrid you have to win every game,' Giggs said.
'It's just getting that balance right, how many minutes he plays, whether he misses a game, and what's best for us and Real. Obviously, ideally I want him to play every minute of every game.
'We do a lot of work between camps logging the minutes certain players have played. Then we are trying to get it right regarding training and game time.'