Scotland lie fourth in the Italy-led Group Five, two points behind both the second-placed Norway and Slovenia, who they meet in Celje next Wednesday. Belarus are second from bottom, with key players reportedly at odds with the coach Anatoly Baidnachy, yet Weir warned against taking victory for granted.
"I've read that they are struggling," the Everton captain said, "but it's all about our level of performance. We're not at the stage where we can turn up and play at 80 or 90 per cent and expect to win. We have to concentrate on achieving a result.
"If you don't perform for 45 minutes, or even half an hour, you can be caught out. Things change so quickly in football. We've shown at Everton this season how they can turn, because whoever you play, there are players out there capable of exploiting weaknesses."
Weir, along with Christian Dailly and the injured Jackie McNamara, is one of only three current Scotland players to have appeared in the finals. At the start of the qualifying series, the 35-year-old defender was in international retirement after falling out with Berti Vogts early in the German's ill-starred reign. Once Smith took over, however, he returned and has played a prominent part in the Scots' revival.
"In Walter's five games, our performance level has gone up each time," he said. "The feel-good factor is there. I've experienced it before - we qualified in 1998 under Craig [Brown, Vogts' predecessor] and got some decent results in England, Germany and Holland - but there hasn't really been a good campaign for a while.
"Now it would be a disappointment if we didn't earn a play-off. Second place would be a huge achievement given where we've come from, but we've given ourselves a chance. Playing in a major tournament is better than anything in football. It's what you play for. They're memories you'll have for the rest of your life and it's something I want to do again."
It is debatable which would have been less plausible as 2005 began: the prospect of Scotland contesting a play-off, or Weir wearing the dark blue again. "My enjoyment [in playing for Scotland] had largely gone. I think a lot of the lads would say the same. Everyone wondered where we were going and how to get out of this mess.
"Walter has turned it around in a short time and deserves massive credit. Communication and organisation have been spot on. He has taken all the excuses away - we had this thing before about the press being against us. He has also treated us like adults, and people respond to that."
Referring to the previous regime, but resisting the temptation to use Vogts' name, Weir added: "People weren't turning up to play for whatever reason, which was a bad start. Now they're not dropping out. They're turning up desperate to play and are disappointed if they don't. That's how it should always be. The fact that it wasn't tells you there was something wrong."
Even so, if Scotland are to keep their campaign alive, they must rely on Norway failing to win one of their remaining fixtures while taking maximum points themselves.
"The only certainty is that we won't finish second if we don't win our two," Weir said. "The worst scenario would be other results going for us and us not doing our job. But we can't worry about results elsewhere. Our focus must be solely on Belarus."
Meanwhile, Smith responded to Age Hareide after the Norway coach suggested that Scotland do not create enough chances to win both games.
"I'd have thought at this stage he would have been concerned about his own side," the former Rangers and Everton manager said. "Three shots and three goals in the last two matches? Fair enough, but we scored two in Oslo, and I seem to remember we made more chances than Norway."Reuse content