I don't think there is any chance to call Lazio a weak team. They finished fifth in the points table last season as well. So I think Lazio is a strong enough team. This season too, they have performed well in the first two matches.
The important thing is that this is Lazio's home match. Lazio is unbeaten in their last 3 home matches against Bayern. Won two home matches and drew one. So I think this match will either be a draw or Lazio will get full points. A draw seems more likely to me
Lazio is not a weak team, they played quite well and were consistent last season. Lazio also has a chance to win in the match against Inter.
but Inter themselves are now in much better form. Lazio must be wary of Martinez and Lukaku. and more importantly a very strong Inter midfield so far.