Overall, Juventus are the favorites, and what is a little doubtful about them is the inconsistency they often show. This is a home match for Sporting and usually the team that acts as the host will play all out, moreover they are only 1 goal behind in the first leg. I want to see what strategy Juventus will play in this important match.
It looks like the second leg matches for Juventus and Sporting will also be more interesting to watch because what you said might be true if the home team (Sporting) will try to outperform Juventus even though they are one goal behind on aggregate. And Juventus themselves must also have a pretty good strategy in this second leg because Juventus must know that the home team will play better to ensure they qualify for the next round.
Juventus must be able to maximize all the opportunities that exist and they cannot survive even though they have a slight aggregate advantage because that could be an opportunity for Sporting to turn things around in the second leg later if Juventus are caught off guard. Juventus must manage the rhythm in a balanced way so that every ball possession they get can be a good capital to make Sporting even more frustrated.
In the first leg before that, we knew that there was a very surprising incident, the Juventus goalkeeper Wojciech Szczęsny experienced palpitations in that match and it seems that many media have confirmed that this was fine for Wojciech Szczęsny. It looks like Juventus will continue to play with the main squad with their flagship goalkeeper and Sporting's chances of winning are still relatively small. But here I will still favor Juventus to advance to the semifinals.