Just three players – Davinson Sanchez, Ben Davies and Sergio Reguilon – retained their places from Sunday's 3-3 Premier League draw with West Ham as Spurs got their European campaign underway on Thursday.
But there was no lack of fluency on show as hosts Tottenham raced into an early two-goal lead before putting a seal on the victory in the final 10 minutes.
Spurs head coach Mourinho was understandably delighted to have seen his team earn such a comfortable victory in London.
"I'm happy for the squad," he told BT Sport. "We believe in the others because the others work so hard to play and be ready.
"Normally I wouldn't do it for the first match of the group phase playing at home, you want to make sure you get these three points, but I trust the boys and the answer was good.
"Not a magnificent performance but solid and safe."
Mourinho's changes meant he was able to bring the likes of Son Heung-min, Dele Alli and Giovani Lo Celso off the bench in the second half against LASK.
Portuguese boss Mourinho admitted he is finding it difficult to leave so much talent out of the starting XI but compared the situation favourably to last season's battles with a lengthy injury list.
"It is hard because I feel for them. Of course everybody wants to play and for the boys it's a bit frustrating," he added.
"They fight to have more minutes and in the end not everybody can play, but it's great. Last season I had lots of problems with no striking force and not even wingers or attacking players in some periods of the season.
"Now we have this amazing squad and with UEFA allowing to have everybody on the bench, I look to my side and I have so many options."
Mourinho went on to share his belief that Spurs would have earned a more comfortable win over LASK had supporters been present.
He continued: "Yeah, we could [have scored more], but it's not a knockout game two legs, it's just about the three points.
"Of course, it could be more, I believe with supporters in the stadium it would be more because then they push and bring that extra bit of energy. But in the end, opportunities for people to play, to get confidence, three points and that's a good start."