Martinez has already signed Antolin Alcaraz, James McArthur, Mauro Boselli and Ali Al-Habsi this summer.
“There is still a long way to go before the [transfer] window closes,” Martinez said.
“I expect a few people to come in and hopefully we will balance the squad and be a stronger group of players than we were last season.
“We want to create a very competitive environment at Wigan Athletic and to do that we need to improve the squad in every window.
“We will do that and we are always working to do that.”
