Celtic's chances of beating Benfica in their Group G opener at Parkhead later this month looked to have increased after midfielder Axel Witsel joined Russian side Zenit St Petersburg in a transfer reportedly worth £32million while Javi Garcia completed his transfer to Manchester City for a reported fee of £16million
Lennon, who has also to negotiate Barcelona and Spartak Moscow as he bids to reach the knockouts stages of the competition, is still wary of the Eagles. He said: "They sold two players in the window, Garcia went to Man City, and the other player went for a lot of money as well. They still have a very strong squad, though."
Lennon added: "They may be weakened by those sales but they are still a formidable opponent. We are going to take one step at a time so our focus will be Benfica.
"We had them watched at the weekend because they are our first opponents and they won 3-0 against Nacional at home. We might try to get another look at them before we play them. We are at home and would really like to win that game and if we could get off to a good start it would really set the rest of the campaign up very nicely."
Lennon will cross his fingers and hope those players who are away on international duty come back unscathed.
The former Parkhead skipper will watch with interest as Scotland begin their 2014 World Cup qualifying campaign this weekend with a home game against Serbia, followed by the visit of Macedonia on Tuesday night.
The Northern Irishman said: "I think they need to get off to a good start and Serbia, even though they are going through a transitional period, will be pretty difficult opponents.
"But Scotland are capable of winning and if they did that would be a great boost and get the campaign up and running.
"And what a start it would be if they could do (get six points out of six). Winning the home games are vital and if Scotland can pick things up away from home you never know where it could take you. But I think it is imperative you win your home games."