The England left-back is out for up to six weeks after fracturing his toe in the Merseyside derby and Martinez is expecting others to stake their claim.
"When something like this happens it's an opportunity for other players and can give them excitement," he said.
"Obviously you never want to lose players to injury but unfortunately it's a contact game and that will happen.
"We've had players who have worked hard for five months and deserved an opportunity in the team so they will get that.
"I'm really excited to see how we react as a team and a squad to the demands ahead. It's there for us to try and fulfil our potential."
Baines has 18 months remaining on his current deal and Martinez is determined to fend off any renewed interest from Manchester United.
"I think the injury doesn't change anything," he added. "All our plans have always been the same. We want to have Leighton for the long term and that will never change.
"The injury is a setback as you can imagine but we will use it to regenerate him, to give him a bit of a breather as he has been playing week in, week out and has had a lot of big demands on him because he's been playing international football also.
"It is a period we are going to use in our favour but, in terms of his contractual situation, it will never change what our thoughts were and our strategy behind the scenes."
Martinez also said he wanted to keep Tony Hibbert at the club, with the defender's contract due to expire next summer.
"Tony Hibbert and (fellow academy graduate) Leon Osman are unique characters," he said.
"They are more than players, they represent the club and give direction to the new players coming in, youngsters and foreigners.
"Tony is someone I want to have at the club as long as we can. Another aspect is to see how he is after the injury. All he wants is to focus on his fitness and fight to earn a place in the team.
"I didn't think it is the moment to look any further. He is a gem of a person, a special person to have at a football club."