The substitution took place in the 51st minute when Geoff Cooke, the former England manager and now director of rugby at the Second Division club, brandished numbered cards on the touchline, bringing Cassidy on for Judd Marshall.
The International Board introduced substitutes from yesterday to make the game more attractive and to prevent players feigning injuries and Cooke, typically, was on the ball - though his decision did not alter the flow of the game.
Bedford were able to get the ball to Martin Offiah only once and the speedy wing sprinted in from 50 yards to make the score 22-28 in the 56th minute.
But the South Africans were running in regular tries and kicker Louis Koen landed all the conversions plus a couple of penalties. The Junior Springboks were always in control of the match, although they needed a late try from the winger Chivago Breda before clinching their victory.
Andy Reed, the Scotland lock, yesterday became the latest casualty of the club versus country issue. The Wasps forward was originally named in the squad for the Scotland A match against South Africa A at Hawick on Friday night but is needed for his club's Anglo-Welsh League game at Pontypridd tomorrow.
George Graham will miss the Scotland A game through injury. The former rugby league forward was selected to play against Australia last Wednesday but had to withdraw because of a calf injury.
The Scotland A squad shows several changes to the 21 on duty last Wednesday for the Australians' opening tour match in Scotland. The significant newcomer among the backs is the wing James Craig, while also in the squad is Watsonians full-back Derrick Lee. In the forwards, there is promotion for locks Stuart Grimes and Scott Aitken and a recall for the prop John Manson.
Injury-hit Australia will field their trainer, Dirk Williams, in the side to play the Scottish Districts Select XV at McDiarmid Park in Perth today.
Scotland A squad, Scotland Districts team, Digest, page 25Reuse content