The NFC North side, who won three of their four pre-season games, scored just two rushing touchdowns in August, while starting quarterback Matthew Stafford completed only one touchdown pass.
The wide receiver, who broke the single-season record for receiving yards in 2012, told the team's website: "I don't think people should panic about the offense's performance during the pre-season. I think we just have to be smarter.
"Whenever you have drops and guys not being where they are supposed to be at, that can all contribute to us not making plays down the field, moving the ball down the field, getting into the redzone and scoring.
"I think guys really have their focus cap on this week. We had a good practice today to start off our week right. Guys are focused and I think that will carry over."
The Lions begin their season against the Minnesota Vikings on Sunday.