Shaw was speaking after defeat to Crystal Palace on Saturday.
“We have a very good group," said Shaw.
"But personally I think we need more players to strengthen the squad.
"It can give us a boost.
“When you look around at how other teams are strengthening their teams, then we must also do it to keep up with the others.
“The pre-season we've had together is not the way it should have been. We've had a week all together.
“We haven't been able to prepare in the way we wanted and that's not an excuse, because we have the quality of players to be able to win games like this, but we weren't up to it."