I agree with you that Lazio would win against Juventus when they play on Saturday at Lazio's home. Since Juventus lost the Italy Serie A title race to Inter Milan, Juventus has not been consistent in the league, and because of that, AC Milan overtook Juventus to occupy the second position in the Italy Serie A table.
This could indeed happen again to Juventus this week, although this is something that Juventus fans don't want at the moment. Because, however, Juventus will also continue to fight to win this match in order to no longer lose its position in third place, even though this will not immediately disappear for Juventus if it really loses to the home team Lazio. However, it will still be very important to maintain it because the match has not yet started and Juventus itself can still improve itself from now on.
Nothing will happen completely as you imagine, even though lately Juventus have had bad results and also Juventus who will only play away against Lazio. But still, basically Juventus still has better quality compared to Lazio. After all, Lazio is also always difficult to beat Juventus every season and yes, because Juventus has a good trend against Lazio every season then I think any result in this match is likely to happen and does not make 100% victory for Lazio. After all, playing at home also does not fully promise victory and therefore, Juventus will still have a good chance to get points in this away match against Lazio because after all, Juventus is also not a mediocre team.