When Louis and Jean-Baptist arranged a transfer to KSK Beveren in 1965, the younger brothers Jean-Marie and Toon also made the switch to the Waasland club.

[5] At the end of the 1971–72 season, Aged 18, Pfaff made his debut for the fist team of Beveren in the Belgian First Division.

The club became national champion for the first time in its existence, with Pfaff not conceding a goal in half of the matches (17).

[9] Beveren reached the Belgian Cup final again in 1980, after a brilliant performance by Pfaff in the return match of the semi-final against Standard.

[11] After the 1982 FIFA World Cup, the 28-year old Pfaff moved to the German top club Bayern Munich for a transfer fee equivalent to 400,000 euros.

[12] In Munich he didn't only discovered a new football culture, but he was also exposed to the immense pressure of an absolute top club.

Despite a false start in his debut match at Bremen (he underestimated one of Uwe Reinders' famous long throw-ins and rebounded the ball into his own goal), Pfaff quickly became an indispensable link in the team.

[14] Due to his performances in the second half of the season, Pfaff was named a world-class goalkeeper by the leading magazine Kicker in July 1983.

In the penalty shootout, Michael Rummenigge scored the decisive goal after Pfaff had saved Norbert Ringels' attempt.

The final of the DFB Pokal was reached again, but the match in the Olympiastadion in Berlin was surprisingly lost 1–2 against Bayer Uerdingen.

[19] In the first half of the 1985–86 season, Pfaff was plagued by injuries, even lost his starting place at Bayern and had to fear that he would not be in the Belgian selection that was qualified for the 1986 World Cup in Mexico.

[15] The 1986–87 Bundesliga was convincingly won by Bayern for the third time in a row, eventually ending with a 6 point lead over Hamburger SV.

In the return match at the Bernabeu stadium, Real Madrid were also unable to make up for their heavy 1-4 defeat in the first leg.

The Turkish Cup final turned out to be the last professional game for Pfaff, as he decided to end his 18 year long-career as a goalkeeper in 1990.

[28] In 1976, the new Belgian coach Guy Thys decided to rejuvenate the Red Devils' selection for the 1976 European Championship.

[29] He did his best, intimidated Johan Neeskens in front of the Italian referee Alberto Michelotti, and made sure that he missed a penalty.

The Red Devils took the lead thanks to a goal by Roger van Gool, but then the Netherlands equalized through Johnny Rep and Belgium eventually lost 1–2 after a nice lob by Cruijff.

“Nobody understood me, he explained later, but Cruijff had scored a beautiful goal and my sense of sportsmanship forced me to give him a compliment.”[30] In the national team, Pfaff was a key player in the 1980 European Championship in Italy.

Pfaff, who was called 'El Simpatico' by the Mexican football fans, played at a high level with great saves (especially against the Soviet Union in the eighth final) and reached the semi-finals with his team.

When I see Maradona dribbling past our entire defence, I think that if there had been a man like Ludo Coeck, Diego would never have been able to achieve such a feat."

[34] Despite his sturdy physical build, Pfaff possessed quick reflexes and was known for his spectacular playing style, as well as his ability to produce acrobatic saves, which made him an effective shot-stopper.

He was also known for his extroverted and outspoken character, his lively and eccentric personality, and his strong and charismatic leadership qualities, as well as his confidence, fair-play, and professionalism, which made him an excellent organiser of the defence and a popular figure among the fans; as such, due to his cheerful attitude on the pitch and humorous demeanor, he earned him the nickname El Simpático ("Mr. Nice Guy," in Spanish) during the 1986 World Cup in Mexico.

He also excelled at quickly rushing off his line; moreover, although he was not the tallest goalkeeper, his large hands aided him when coming out to claim the ball, which made him an authoritative presence in goal.

The "Belgium of the eighties" squad faced a selection of world stars, including Franz Beckenbauer, Ruud Krol, Michel Platini, Roger Milla, Alain Giresse and Søren Lerby.

Pfaff became a member of BFC Dynamo and promoted the establishment of a new youth sports school at the club.