"He's one of the few people around who tell things straight to your face," Riquelme once said of his encounter with the Dutchman, who has led Bayern to within touching distance of a unique Bundesliga, Cup and Champions League Cup treble.
"On the first day, he sat down with me at a table, he told me that the president had signed me and not him and that he hadn't asked for me, so it was immediately obvious to me that I wasn't going to play.
"But I prefer people who are like this. The man was very sincere and I learned from the experience."
Van Gaal, whose Bayern team effectively wrapped up the Bundesliga title on Saturday with a 3-1 win over VfL Bochum, is one of the sport's most colourful coaches - sometimes literally, as he loses his temper during interviews and his face goes progressively redder with rage.
He was involved in a memorable exchange at Barcelona, telling one reporter "you are really bad" over reports that he had broken a dressing room door during a row with Brazilian playmaker Rivaldo.
The room filled with laughter as Van Gaal lost his cool and mixed up his Spanish in the process.
His coaching career has seen some miserable failures, the most glaring of which saw him fail to qualify a Dutch team brimming with talent for the 2002 World Cup in Japan and South Korea.
Riquelme and Rivaldo, who both found themselves out of favour during Van Gaal's tumultuous three-year stint at Barcelona in the late 1990s, are among two top players whose talents Van Gaal has failed to appreciate and Italian World Cup winner Luca Toni joined the list at Bayern this year.
RAW TALENT
Yet, the Dutchman, with his distinctive quiff, has also a knack for plucking out raw talent.
His Ajax Amsterdam team which won the Champions League in 1995 was brimming with young players and his decision to put his faith in Carlos Puyol at Barcelona has paid divideds both for the Catalan club and the Spanish national side.
At Bayern, he has overseen the emergence of Thomas Muller, among others.
The 20-year-old capped his season with a brilliant hat-trick on Saturday which left Bayern three points ahead of Schalke 04 with a goal difference which is an uncatchable 17 better than their rivals.
When Bayern complete the formality of wrapping up the title at relegated Hertha Berlin next week, Van Gaal will have won league titles with four clubs in three countries, following Ajax and AZ Alkmaar in the Netherlands and Barcelona.
"For me this is a very big achievement," he said after Saturday's game. "I don't think many coaches in Europe have had the luck to be champions in three countries, I'm one of the few, I've done it in very good football countries and I'm very proud.
"May be now I should look for another country."
He will also have a chance to become only the third coach to win the Champions League with two different clubs when his side meet Inter Milan in Madrid on June 22.
Sometimes labelled arrogant, Van Gaal refused to accept thecredit of the younger players, instead praising his coaching staff.
"I think the credit must go to my assistants. I am the coach and the players make themselves," he said.
But even his year in Bayern has not been trouble free. Early results were poor and Van Gaal, with expensive signings such as Arjen Robben and Mario Gomez at his command, had to withstand intense speculation over his future.
But the season turned when they won 4-1 at Juventus to reach the knockout stages of the Champions League and Bayern have not looked back since.
"Bayern Munich is the best club I haved worked at in terms of organisation," said Van Gaal. "We have some great possibilities here."
