"Kieffer's got to be aware of that," Giggs said. "In European football some referees see it as too physical.

"It's frustrating. I thought decisions went against him and some referees might let it go.

"Kieffer got booked early so I think that stopped the physicality aspect.

"I also thought he got fouled on the edge of the box which didn't get punished."

Moore has been a pivotal figure for Wales since breaking onto the international scene in 2019.

The 28-year-old has scored three times in nine games, and much of Wales' build-up play has been based on using his considerable physical attributes and aiming high balls towards him.

Giggs – who will also be without suspended midfielder Joe Morrell in Sofia – accepts Wales will have to modify their attacking approach without Moore.

"We've got Tyler (Roberts) and we've got other options as well," he said.

"We'll look at how Bulgaria set up (in Sunday's 2-0 defeat to Finland) and see how we can exploit them.

"Our approach will be a little bit different and we'll see what we feel will be best in Bulgaria."

Wales top their Nations League group at the halfway stage with seven points from nine and are a point clear of second-placed Finland.

The Dragons have yet to concede in the competition but have managed only six on-target goal attempts and two goals in their three games.

"We have to show a little bit better composure," said Giggs, who revealed injury and illness had restricted the time that attacking trio Daniel James, David Brooks and Harry Wilson have spent on the training pitch.

"We have to get players on the ball quicker, and when we do that it's about decision-making and execution in the last third.

"It's a tight turnaround for Bulgaria and we knew it would be tough. We have a few players who aren't 100 per cent fitness-wise and three away games is a lot of travelling.

"But we'll be ready and a couple of players missing gives us a chance for other players to come in, we'll look to freshen it up and improve on Wednesday.

"I'm obviously delighted after the three games. You have to be happy with seven points out of nine."