Spurs saw key players Luka Modric and Rafael van der Vaart sold while Ledley King was forced to retire with the likes of Clint Dempsey, Mousa Dembele and Jan Vertonghen brought in to replace them.
Six players were signed by Andre Villas-Boas while 11 first-teamers left and Defoe admits it was an uncertain period at White Hart Lane.
"It was a bit mad," the 29-year-old told reporters.
"You walk into the changing rooms, see the lads and don’t know if you’re going to see them the next day.
|15/2||Tottenham are 15/2 with William Hill to beat Reading 2-1
Spurs are yet to win a Premier League game this season, having lost one and drawn two, but Defoe is unconcerned, insisting it will take time for Villas-Boas' methods to be implemented at the club.
"When a player joins a new club it takes a while to bed in. It is no different for the manager," he continued.
"When the new manager comes in, straight away you are going to be under pressure. It takes time. It is still early days and it is important to give managers a chance.
"We have got a good, strong squad and I’m sure it will be fine.
"People say it is the same personnel but it is a different way of playing, a different system this year, so that is going to take time.
"A lot of the boys haven’t played like that before. It is going to take time but I’m sure we will adapt and it will be fine.
"In my opinion, I think the manager is really good, really organised. Training has been fantastic, he knows exactly what he wants.
"I honestly think he will do well. He just needs a little bit of luck and then we will be flying."
Defoe is in line to pick up his 50th England cap in the upcoming World Cup qualifiers against Moldova and Ukraine, despite only ever starting 17 times for the Three Lions.
The forward, who netted in the recent friendly win over Italy, is looking forward to the occasion, while stating he feels in good shape.
"It will mean the world to get the 50th cap," he added. "It’s something I’ve been thinking about for a while, speaking with my family about. It is a good achievement.
"I was happy when I went to the Euros and to get the goal against Italy was good for my confidence. I feel sharp and ready to go."