The Spain international is poised to leave the Camp Nou - reportedly to join AS Monaco - but wrote a letter for the club to publish thanking those he has worked alongside and under over the past 12 years since his first-team debut in 2002.
Valdes made his Barcelona debut under Van Gaal, who is poised to be named as David Moyes’ successor at Old Trafford in the forthcoming days, and the 32-year-old thanked the Dutch coach “for backing what only he could see in him.”
The outgoing goalkeeper also credits Van Gaal for laying the building blocks for the most successful Barcelona side in history - a team that won six La Liga titles and three European Cups amongst a host of major honours from 2002 to the present day.
"He (Van Gaal) began building this historic Barca side, which I have been privileged to be part of," Valdes wrote in his letter.
Van Gaal also handed Barcelona superstars Xavi and Andres Iniesta their first-team debuts during an earlier spell at the Camp Nou - and Manchester United supporters hope the vastly-experienced 62-year-old will spot some unearthed gems in the Red Devils’ youth teams over the forthcoming seasons.
Manchester United will confirm Van Gaal, who has decided to quit his current job as Netherlands head coach after this summer’s World Cup finals in Brazil, as their new permanent manager either on Thursday or Friday.