Yorke came on as a half-time substitute for Rovers at The Hawthorns and scored their opening goal in a 2-0 win.

But he was forced off five minutes from the end with the recurrence of the hamstring trouble that kept him out against Leeds last weekend.

Souness said: "We have two games coming up - away to Sofia and Spurs at home on Sunday.

"He'll certainly miss them, but hopefully he'll be ready to return after the break.

"It's a blow to us because hamstrings are dodgy things. He pulled up just when I thought he was about to play Andy Cole for a third.

"I asked him afterwards if it was any worse than before and he said 'no, it's about the same'. But this time we will have to give him more rest."

Souness felt Rovers were well worth their win. "We had a good night but we had to work hard for it.

"We knew it would be a hard physical battle. They are in your face with their football, but I felt we matched them in that department.

"It was a good performance. We defended well and weathered the storm. We were always going to create chances and we took them when they came."

Baggies boss Gary Megson refused to blame Blackburn's controversial opening goal for his side's defeat.

"Even if it was not a penalty, it deserved to be one on the defending we showed. Some of it was despairing stuff," Megson said.

"We never got out of first gear. We never played the way we are going to have to play if we are going to get results.

"Hopefully it was just something gone wrong on the day."

The Baggies have made a solid start to the season, earning nine points from their opening eight games.

But Megson warned his players: "All teams who come up get an initial burst of enthusiasm and then it settles down a bit, but it is something we need to get back if we are to get results.

"We have now played eight games and got nine points. We could have had one or two more, but we are not going to get more if we play like that."