I think Juventus are still under a big threat by Sporting in this round. Because despite getting that win with a 1-0 score in the first leg they are still not in a very advantageous situation. Sporting performed very well in that match and Juventus were really lucky to not even lose that. Juventus somehow managed to do their usual trick and secured a 1-0 lead until the end of the match. But they might have bigger difficulties now.
Because Sporting are going to play before their supporters above all else. This can give them extra confidence about a comeback in this round. Besides if they can manage to be even more in control of match this time they can score an early goal to take the lead too. Juventus will need to do their best defending here. As things aren't going well in the Serie A for them they really need the win the Europa League title to be able to qualify for the Champions League again.
1-0 aggregate advantage will not make Juventus comfortable. Sporting is not a weak team. although at the moment Sporting is also not a team that is at the top of the Premeira League standings. but indeed the quality of his game is good enough to face Juventus.
when Sporting plays at home, for sure they will dominate possession more. but it all depends on how the strategy will be used Juve. because Juventus certainly studied Sporting's game from the first leg, even though they won, Sporting did make it difficult for Juventus.
Sporting are always performing well when ever they are playing match in Europa League, and this give me impression that they have chances of defeating Juventus. Juventus are seriously struggling and I know it is not just in Italian League, it is something Sporting will use as advantage to win.