The Lions are going to let that competition play itself out over the course of training camp and the preseason.
"I don't want to put a timetable on it, but we're going to look for consistency over a period of time," Schwartz said when asked about the competition between veteran Ashlee Palmer and second-year players
"It is not going to be one we will decide tomorrow. We are not looking for flash plays. We are looking for players that can be reliable for long periods of time."
Palmer seemed to be the favorite heading into training camp – and still might be – but Lewis and Whitehead have shown early in camp that they're way ahead of where they were as rookies and have made that competition one of the better ones in camp.
It very well could, but still, some question marks will linger after it's all said and done as to how improved the Lions will be at linebacker this season.
It certainly helps to have Tulloch back healthy after he delay with knee tendinitis all of last year, but there will be a certain amount of unknown entering the season with three relatively inexperienced players vying for the one open spot.
Palmer, 27, is the most experienced of the group, but still has only nine starts.
Whitehead might have made the biggest leap forward since last year, but he also had the furthest to come.
"Last year he was trying to learn how to play linebacker," Schwartz said. "Last year he knew how to play at the line of scrimmage, but we don't play at the line of scrimmage very much. It was a big change for him, but he has a year under his belt.
"What happened with a guy like Tahir, he learned and improved over the course of the season. He continued that this offseason."
Whitehead played outside linebacker in college and did play a lot at the line of scrimmage, but said he played wide and out in space at times, which has made the adjustment to the Lions' 4-3 a little easier.
"This year I'm feeling a lot more confident within myself and I think my teammates are starting to feel a little more confident in me and that's my main goal," he said.
Schwartz has made the guidelines to winning the job pretty simple to follow. Whoever does is better for longer will win.
That's not to say the two who don't win a starting spot won't have a role.
"Even if a guy doesn't earn a starting job, there are other opportunities within our defense," Schwartz said. "We have short-yardage packages, goal-line packages."
There is also special teams, which all three players are taking part in in some way, shape or form.
Whatever the role and however they divide the reps, in the end, consistency is going to win out in the search for that starting linebacker.