Three years. That’s the amount of time Dirk Nowitzki believes he has left in the NBA. He admitted that during the early part of the 2013-14 season. He said he felt he had about “10,000 to 15,000 good minutes left” in him. Take his career average of 2,850 minutes per season, and you figure Nowitzki has about three years left.

The Mavericks’ season ended May 4 in San Antonio, and Nowitzki is a free agent this summer. He has made it clear he wants to win another title. He also made it clear when talking to reporters on Monday in Dallas that he wants to stay in Dallas and make one last run, even at a “hometown discount.”

“We’ll find a good way where I feel respected for what I did, and where we still have enough money left for us to bring great players in,” Nowitzki told reporters.

The Mavericks reached the postseason after a one-year absence. They found Nowitzki a young running buddy in Monta Ellis, who took some of the scoring load off of Nowitzki’s shoulders.

They pushed San Antonio to seven games and did what few teams have been able to do in recent years — confound San Antonio coach Gregg Popovich.

He admitted after the Spurs trounced the Mavericks in game 7 that head coach Rick Carlisle’s defensive strategies for the first four games of the series bewildered him and his staff until they were able to figure it out.

It was defense that did Dallas in as it lost game 7. They were unable to keep up with the Spurs, who played the best game of their series when it mattered most. But it looks like the Mavericks made progress, right?

It sure looks that way. But there is a problem with this team: They’re old and slow.

NBA analyst Jeff Van Gundy saw it during Sunday’s game. Carlisle commented on it at the start of this season. The Mavs must get younger. The Mavs want to be a contender right now to keep Nowitzki happy. Those two concepts don’t always mix.

Seven players logged an average of at least 20 minutes per game this season. Ellis is the only one under the age of 30. Six of the heavy rotation players on this team are at least 31. Four of them were starters the entire season, including 35-year old Shawn Marion. Vince Carter, now 37, was the first player off the bench. Devin Harris, 31, missed half the season with an Achilles injury put played plenty when he returned.

It’s fine if you have a couple of role players in their mid-30s. But not six of your top seven players.

The Spurs have an aging trio in Tim Duncan, Tony Parker and Manu Ginobili. But they’re surrounded by young talent that assumes more of the load than the Mavs’ young crop of players.

Nowitzki, Carter and Marion are only going to get older. All three want to come back to Dallas next fall. Nowitzki is the only guarantee. And none of these guys is suddenly going to become old and quick.

As for getting younger? The Mavs have no first-round pick, thanks to the Lamar Odom trade three years ago. They still have their second-round pick, and they could find another Jae Crowder. But these Mavs need a much more dynamic player, and their track record for finding those players in the second round is, well, let’s say it’s not good as San Antonio’s.

At least the Mavs have money to play with. They’re looking at least $30 million to spend on free agents. That looks great, except you’ve got to pay Nowitzki, and perhaps Carter and Marion, if you bring them both back. And you have to consider brining both back because when you look at what could be out there in free agency, it doesn’t exactly make the earth move.

Sure, players like LeBron James and Carmelo Anthony could opt out and test the market. But that seems highly unlikely.

If you’re planning to spend money and you’re hoping to get younger, you’re looking at gambles, such as the one that the Mavs took on Ellis last summer. That certainly worked out. But there are no guarantees.

So what are Mavs owner Mark Cuban and team president Donnie Nelson to do? They must dance a delicate dance this offseason, finding the right free agents, infusing the team with whatever youth they can find and making sure they keep Nowitzki in the process.

“We’ll just have to wait and see how the summer goes,” Nowitzki said. “There’s a lot of cap space. Donnie and Mark are probably gonna go to work. We’ll go from there.”

Because old and slow only gets you so far in the NBA. Like a first-round playoff exit.