Williams, who earned his first Bafana Bafana cap in March, was rumoured last week to be on the radar of Villarreal, who have been impressed by the shot-stopper’s performances this season, prompting the Spaniards to enquire about Williams’ services.
“Yes, he will go, if it’s there (an offer) he will go… there’s no way I will stop him, I’ll never stop any player,” Johnson said at the weekend.
“Ronwen is a good player, I see him in the next four or five years being the next South African number one… all he has to do is push himself.”
The 22-year-old was named Goalkeeper of the Season in 2013 and was forced to reproduce that form this season, due to an ailing defence at United, which left Williams exposed on many occasions.
The Pretoria club finished the season fifth in the Premiership in Johnson’s first campaign in charge.
“It’s a step up (in Spain), it’s a better environment, it’s something else and that is important that players understand that,” Johnson said.
“That, for me, is always an enhancement or a boost for the player that’s involved.
“When you have those type of things that say he’s going to play overseas, for a trial, it’s nice to have because he is going somewhere where the football is better, the training could be better.”
El Submarino Amarillo (The Yellow Submarine) are currently seventh in the Spain’s top league and have a single fixture left this season.
An envious Johnson admitted he would not hesitate at the chance to play abroad and urged Williams to jump at the opportunity.
“He’s going somewhere where we all want to go. I’d like to coach Villarreal and if they ask me, I’m going to go as well for a trial.
“It’s about giving our players that little bit of energy.”