The Lions prop was already expected to miss the opening game of the series against Australia on Saturday due to club commitments with Northampton.

But the 33-year-old has now suffered a recurrence of the knee problem which forced him to pull out of the Saints' European Cup win in Glasgow just over a week ago.

Smith told The Scotsman: "When I first did it in the game with Sale two weeks ago, it seemed like just a hyper-extension and, although it kept me out of the Glasgow game, I felt fine on Saturday against Llanelli and was okay on Sunday.

"But it felt a bit funny in the airport when I flew up to Scotland on Monday and that was when I knew there was something up.

"I've spoken with people at Scotland and Northampton and, while I'm getting a scan now, it looks like a minimum of three weeks out and, possibly, as much as six. It's disappointing and the worst timing."