Janssen only joined Spurs in a £17m move last summer, but he was made available for transfer in the closing stages of the summer window as Tottenham stepped up their pursuit of Fernando Llorente.
The Dutch striker is expected to be behind both Llorente and Harry Kane in the pecking order for Mauricio Pochettino this season, and Lopez revealed that he was on Lille's radar before last week's deadline.
"I offered Marcelo the chance of bringing in experienced players, he didn't want them. We offered him [Wilfried] Bony, for example. He wanted a group that corresponded to his needs," Lopez told SFR Sport.
"He wanted a group he had chosen with [sporting director] Luis Campos. Janssen? Technically, his style of play didn't fit into the project Marcelo wants to create."
Janssen scored just two goals in 27 Premier League appearances for Spurs during his debut season in English football.