With Fernando Torres out for three weeks, the Chelsea boss is left with just two fit first-team strikers, while the Belgian has scored three times in just two games for Everton.
Mourinho currently has Samuel Eto'o, Demba Ba and Fernando Torres on his books up front, although the latter has been ruled out for three weeks with a knee injury, and all three have failed to score in the Premier League so far this season.
Lukaku, meanwhile, has added to his 17-goal return for West Brom last term with three goals in two appearances for Everton, with Roberto Martinez confirming that Chelsea is unable to recall the Belgian forward until the loan is expired at the end of the season.
When asked if he regrets sanction the move, Mourinho told reporters: "No. It is one thing to play for Everton and another to play for Chelsea."
Saturday's 1-1 draw with Tottenham extended Chelsea's run to just one win in four league outings, with the club currently four points adrift of league-leading Arsenal. Mourinho feels that the club, along with Manchester United, was dealt a harder fixture list for the opening round of matches and has called for patience.
"Every weekend someone can lose points. In relation to my team at this moment we are not strong enough to be dominant in every match and win consecutively. That is my point of view," Mourinho said. "I think the league will be open until the end. At this moment some teams are being helped by the fixtures, some are more difficult than others. This season can go all the way, and I think that is good.
"Manchester United have the most difficult one, immediately followed by us. I think by the end of November, that is the moment we will find out somebody is in a little bit better situation than others.
"What I like is my team to be active and not reactive. In the Champions League in the week, the team wanted to be active. This is the mentality I want and I always think it is more difficult to change mentality over tactics."