At 36 years old, Dirk Nowitzki isn't supposed to be as good as he was at 30. Or 25. Or even 20.

He no longer dominates on a nightly basis, and that's OK. Now, that will make some of you angry because you'll view it as being critical of Dirk, but it's the truth.

Father Time eventually gets all of us.

He doesn't always have his legs, so his jumper doesn't fall as consistently as it once did. He hangs around the perimeter, so he doesn't get to the free throw line as much or grab as many rebounds.

The Mavs have as talented a roster as they've had in the Nowitzki era, but Dirk, even at 36, remains the focal point. Reid Kelley/NBAE/Getty Images

But Dirk remains in the upper echelon of NBA players, and he can still drop 25 on a given night.

It's just that he set the standard for his performance so high for so long that folks tend to overreact when he doesn't dominate for a few games. They wonder what's wrong with him. The answer is: nothing.

All you need to know is Dirk is still good enough to help the Mavs make a deep playoff run.

In the Mavs' win over the Utah Jazz on Wednesday night, Dirk had 15 points and 14 rebounds, his first double-double since Dec. 17 and fourth this season. Three games ago against the Portland Trail Blazers, he scored 25 as the Mavs rallied for an improbable win.

Coach Rick Carlisle fully understands Dirk's importance to the team's postseason success, which is why he has made keeping Dirk healthy and rested among his top priorities this season, as he should have done.

Heck, it's why the Mavs and Dirk wish he had been able to relax for the next eight days instead of participating in the All-Star Game for the 13th time.

"It is always an honor to represent the Mavericks at the All-Star Game," Nowitzki said in a statement. "This year it threw a little bit of a wrench into my plans, but I am very excited. Even though it was unexpected, I am looking forward to being a part of the festivities in New York."

Dirk is at the point of his career at which winning is the only stat he truly cares about. It's why the future Hall of Fame player is OK making $8 million this season, about half of what Tyson Chandler and Chandler Parsons earn.

And it's why Dirk is fine with playing only 29.8 minutes game, his lowest total since his rookie season.

Carlisle gives Dirk an occasional game off as a testament to his 1,239 games in the NBA and his age, something San Antonio Spurs coach Gregg Popovich has been doing for Tim Duncan, Tony Parker and Manu Ginobili for years.

Carlisle has done it only three times this season, but Dirk has responded well each time.

He had 22 points and 10 assists against the Chicago Bulls, 25 points and nine rebounds against the Denver Nuggets and 25 points against Portland following a day off.

Maybe he should do it more often.

#41 PF

Dallas Mavericks

2015 STATS

GM 51

PPG18.3

RPG6.0

APG2.0

FG%.467

FT% .889

Dirk's shooting ability is essential to the Mavs' spacing on the court and opens up the pick-and-roll and other parts of Carlisle's free-flowing offense.

His presence provides confidence, and he still plays with a swagger we see every time he hits a key 3-pointer or creates an opportunity for a three-point play.

He's terrific in the pick-and-roll because when teams switch, Dirk usually gets a smaller defender who's a lot easier for him to shoot over. And he still occasionally attacks from the key.

No one outworks him, and he remains an efficient player who takes only 14.3 shots per game to score 18.3 points.

It has taken forever, but the Mavs have finally given Dirk enough help that he can choose when to assert himself. For the most part, he's a spot-up shooter these days, but the Mavs don't have any trepidation about isolating him in the post or at the top of the key when the matchup favors him.

Monta Ellis is the Mavs' best player these days, and the offense runs through him. Chandler is the Mavs' most valuable player.

But Dirk remains this team's heartbeat.