Euan missed out due to a minor stmach bug. Also missing yesterday's training session was scrum-half Mike Blair.
Blair is expected to be unavailable again today but medical staff are confident that he will recover from the knee injury in time for the match on Sunday against Romania.
For yesterday's session, team officials were unable to contact the stand-by player, Sam Pinder, the Glasgow scrum half, in time, so they called in Rory Lawson of Edinburgh, to take his place.
Sam will probably train today but team officials emphasised that his involvement is precautionary. They expect Blair to be ready by Sunday.
Hadden and his fellow coaches sat down last night to select the side, but the signs are that he will keep his changes to a minimum after the historic breakthrough win over the Barbarians last week.
One switch is certain: Gordon Ross has broken his hand, so Glasgow's Dan Parks is on course for a recall at fly half.
"We need to win this game," Hadden said in The Times. "We need to make sure we are in the upper echelons off the game so we need to beat a team that are not too far behind us.
"Romania are very powerful up front and play a very old-fashioned style of game with a lot of kicking. If you allow them to impose their game on you, they can be very effective.
Nor did he admit to being unduly worried by the injuries. "We are going to try to select tonight after the latest update from the medics. These injuries are normal for the start of a week," he said.
You can read The Times article here