Lambert believes the result has been a greater tactical flexibility, which has helped his side make a solid start to the campaign and claim wins over Manchester City and Arsenal.
"The good thing is we can change different ways of playing and different personnel," he told the club website.
"They can adapt to whatever we ask them to do.
"It all depends on who we're playing against and what players are fit, but we can try to get a team to win. They did it last year in games.
"They are systems that we did last season. We can adapt. I played three at the back against Manchester City last week.
"Even though it was the first time this season against Manchester City they did exceptionally well and it was pleasing.
"Then we changed it against Hull. But you give them the systems and they adapt. I wouldn't say 4-3-3 set in stone."