Simon Webster clashed heads while Scottish prop Geoff Cross collided with a high Welsh knee and was yellow carded on a stretcher for a dangerous tackle.
Wales took grip of Scotland’s misfortune with four tries as Scotland hit back once in a game that had many similarities to Kingston University’s bruising defeat against Brighton last November.
Winger Webster had continued but referee Alain Rolland forced him off the pitch just before half an hour after being ill on the touchline.
Wales capitalised after the long injury pause caused a break down in momentum and scored twice but failed to take full advantage with two missed conversions.
Scotland finished the first half yards away from the Welsh try line looking for the first time likely to pierce through a well-organised defence but left the field 16-3 down.
An apparent lack of Scottish confidence in the opening minutes of the second half was in stark contrast to the ooze of Welsh pace and options as Wales increased their lead to 18 points.
Wales added to their score as Shane Williams received the ball close to the try line from a ruck and picked his spot in the left corner after Scotland failed to stand tall.
Welsh stand in skipper Martyn Williams was sin-binned later on for an intentional knock-on which had prevented a threatening right-wing Scottish attack.
But Scotland left it too late in picking themselves up as they pushed for last minute tries, the experience of Chris Paterson and the pace of winger Max Evans causing the Welsh defence most problems.

Scotland Head Coach, Frank Hadden, speaking after the game said: “We were going to come strong at one stage it just took us too long to get going.”
He added: “The two guys who really led by example went off injured as a result of their efforts. We were down to 14 men at one point, Wales like the top quality side they are took full example of that and scored two tries.”
Welsh centre Jamie Roberts, named Man of the Match, said afterwards: “I was quite nervous on the bench at the end; they had us on the edge of our seats.”
Wales will need to improve their kicking efficiency when facing England while Scotland will need to keep heads high to make any impression against France on Saturday.
Tries
Shanklin WALES
AW Jones WALES
Halfpenny WALES
Williams WALES
Evans SCOTLAND
Penalties
S Jones (2) WALES
Paterson (2) SCOTLAND
Conversions
Paterson SCOTLAND