Shaw was only 18 when he played a season of club rugby for Pirates.
"It had a big influence on my career." Shaw said. "I couldn't have chosen a tougher environment.
"At that time there were a lot of All Blacks playing club rugby and I learned from the very best. It helped my career."
Pirates did not have any All Blacks but Southern and University A had their sprinkling of internationals, including John Timu, Marc Ellis, Arran Pene, Stephen Bachop, Josh Kronfeld, Jamie Joseph and future Scottish midfielder John Leslie.
The clash with Joseph, now the Highlanders coach, toughened up Shaw.
"It certainly stopped me from getting on the wrong side of the ruck," he joked.
Shaw (38), a member of the winning World Cup team in 2003, is the oldest member of the England squad.
"A lot of people make more of it than I ever do," he said. "I wouldn't say I'm Peter Pan but I don't feel my age."
Four years ago, in France, Shaw was asked if it would be his last World Cup.
"I would suggest I won't be back in 2015," Shaw said.
There is a lot of pressure at the World Cup but that has not stopped Shaw from having fun.
"I'm enjoying it, otherwise I wouldn't try to get out here," he said. "It is a special tournament and only comes round every four years."
The media interest in rugby is more intense and individual players have a higher profile today compared to when Shaw made his international debut against Italy in 1996.
The English team is disappointed by its form in the first two games of the World Cup.
"We are striving to replicate what we were producing in the early part of the Six Nations," Shaw said. "We are not there yet."
Shaw is confident England will produce its best rugby by the time it reaches the harder games.
"We are making steps but we are a bit behind where we want to be," he said.
"Tries will come if we have patience. We didn't have the patience to let the tries come against Georgia last weekend."
The English team lacked discipline in the first two games.
"We are all keen to make an impression and a few of the guys were over-eager to make their mark on the game," Shaw said.
Shaw knows England will be tested by the Romanian pack on Saturday.
"Everyone was expecting free flowing rugby but it was never going to be the case against those first three opponents," Shaw said.
Another problem faced by England is the penalties it has conceded. There have also been two yellow cards.
"The coaches are dealing with it and are doing an analysis on the referees to prevent it," Shaw said.
"It has just been overexuberance and excitement by individuals that has resulted in those yellow cards."