The 36-year-old midfielder left the west London club after 13 years as a free agent and joined new MLS side New York City, which includes a short loan deal with Manchester City.
If Chelsea had given me a new contract it would have been mad not to take it
But the former England international says that he would have remained at Chelsea if the club had offered him a new deal.
“I would have obviously stayed if Chelsea had offered me another year,” Lampard said. “There was no reason for me to leave.
“Yes, I wanted to play a bit more regularly but I’m not stupid. If Chelsea had given me a new contract it would have been mad not to take it at the time.
“It wasn’t that I didn’t think I could still do it. If I felt like that I wouldn’t have gone to City on loan.
“I had a chat with Jose Mourinho and both he and the club were always great with me. The decision was made, and I don’t know who made it.”
Lampard made 648 appearances for the Blues, scoring a club record 211 goals.
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