Ex-Springbok wing-cum-full back Terblanche spent four years playing alongside Williams at the Ospreys and knows just how dangerous the 2008 IRB Player of the Year can be.
"When Shane starts running, you just hope and pray that someone can get hold of him quickly," said Terblanche.
"He is a fantastic runner and we've got to do our best to ensure the Lions don't get quick ball to supply him with. One on one he is almost impossible to stop."
The two players won the Magners League together and played more than 50 times on the same side. And while Terblanche missed out on a Springbok recall this season, he is backing Shane to make the Lions Test team.
"Shane has proved himself through and through for Wales and I would pretty much select him for the Lions Test side now - it really is a no brainer," said Terblanche.
"I guess he needs to show a little bit of form going into the Tests, but his class is permanent. I just hope he doesn't get too much of a chance to shine against me on Wednesday night."
While the 37-times capped Terblanche agrees the Lions will be heavy favourites to make it four wins in a row, he isn't too despondent, even though the Sharks will be without 10 front line players.
"The Lions only tour every 12 years so it is a huge privilege to play against them. We are short of 10 players because of Springbok calls, but it will still be a great game," said Terblanche.
"I remember playing for the Ospreys against the Wallabies in similar circumstances a few years ago and we won in front of a packed Liberty Stadium. That still ranks as one of my greatest rugby memories.
"The attitiude the Opsreys took into that game is exactly what we need to replcate agaisnt the Lions."