WALTHAM, Mass. – Health concerns are becoming a bigger issue with seemingly each passing day for the Boston Celtics.

Not the season or career-ending variety, but the nagging, miss-a-game-here-and-there sort that does a number on the timing and rhythm players covet developing this time of year.

We’re seeing that now with Celtics point guard Marcus Smart who has sprained ligaments in his left big toe which will keep him sidelined for a third straight game tomorrow night when the Celtics take on the Milwaukee Bucks.

Amir Johnson is another player Boston’s medical staff will keep close tabs on as well due to several ankle sprains in the past.

“I’ve rolled my ankle so many times,” said Johnson who has only missed 13 games in the last three seasons. “But at the same time I just played on it. I have to keep doing my work, icing it and the trainers are taking care of it.”

In addition to being a rim-protector, Johnson is also spending more time defending away from the basket in addition to providing some much-needed help defense to his teammates in the backcourt as well as his fellow bigs.

Being able to shift directions quickly is essential to him being an impact defender for the Celtics who come into Tuesday’s game against Milwaukee with a defense that’s ranked seventh in the NBA.

And while there are a number of players who have contributed to the fast start defensively for Boston, Johnson is indeed one of the keys to this unit’s play.

“He’s definitely a good guy to play with,” said Boston’s Kelly Olynyk whose defense has probably benefited more than any other Celtic since Johnson’s arrival this summer. “He (Johnson) plays with high energy, high intensity on both ends of the floor. He makes things happen. He makes things easy, he covers your back. He doesn’t need the ball on offense. He doesn’t sell you out on defense. He’s got your back or he’s there. Oftentimes he doesn’t need help so he doesn’t put you in the position. He’s a great guy to play with.”

The 28-year-old Johnson embraces the fact that his teammates count on him to not only defend his man at a high level, but also help them out, too.

To do so, Johnson has to stay healthy which is why he makes a point of doing all he can to ensure his ankles don’t become problematic and force him to miss time.

“I make sure before practice, before games do an ankle warm-up to make sure my ankles are strong,” Johnson said. “I definitely take care of it.”