Nelson Cruz turned 39 on Monday, but the occasion may mean more to his teammates than to the Twins slugger.

"Nah, it's just a number," Cruz said. "People like to make a big deal about round numbers, not 39."

Maybe so, but reaching that age as an active major leaguer is a big deal. In general, only historically great hitters are still playing at that age; future Hall of Famer Albert Pujols is the only hitter older than Cruz in MLB today.

"Well, he's been doing it a long time, and he's been very, very good [this year]. At the top of his game," said Twins manager Rocco Baldelli, who is 15 months younger than his designated hitter and who retired at 29. "This is kind of who he is. What we're getting from him right now is who he's been for a while."

So it seems. With 16 home runs at the season's midpoint despite missing two weeks with a sore wrist, Cruz is on course to record his sixth consecutive 30-homer season. Only Edwin Encarnacion, with seven, has a longer current streak.

But Cruz is doing far more than hitting home runs. His numbers are All-Star caliber, even if he's staying home next Tuesday. Cruz is batting .284, and with 27 walks and four hit-by-pitches, he owns an on-base percentage of .372. His .572 slugging percentage is the best on the Twins, a formidable collection of hitters, as is his .945 OPS.

His 1.8 wins above replacement (WAR), a measurement that includes defense, ranks eighth on the team, even though the only gloves he's worn are batting gloves.

"He's just so amazing to watch. He's such a smart, disciplined hitter," hitting coach James Rowson said. "He knows what he can do and what he can't, and he just waits for a chance to do some damage."

Cruz's results illustrate how valuable he's been to the team, but the underlying building blocks are impressively solid as well — for a hitter of any age. He makes contact with 68.7% of the pitches he swings at, down only slightly from his career average of 72.4%. He swings at 29.5% of pitches out of the strike zone, lower than any Twins player but Mitch Garver and Jorge Polanco.

And when he makes contact, look out. An astonishing 55.2% of the balls Cruz puts in play are hard-hit, by Fangraphs.com's tracking, a career high rate that's by far the best on the Twins, and trails only Rangers strongman Joey Gallo in the major leagues this year.

You don't have to tell the White Sox. Cruz crushed three home runs over the weekend in Chicago, balls that traveled more than a quarter-mile combined and left Baldelli speechless. "I didn't say anything at all, because when you see something like that, you just take it in and enjoy it," he said of Nelson's 469-foot rocket on Saturday, the longest home run hit by a Twin in the past two seasons. "Nelly is obviously riding one of those great highs right now. He's hitting balls a mile and having great at-bat after great at-bat."

And there is no horizon in sight yet. "I feel good, I feel strong," Cruz said. "I make sure to take care of myself, get my rest. It's a long season, but when you're winning, you want to play every day."

Cruz's contract, which pays him $14 million this season, includes a team option for 2020 at $12 million, a bargain rate that the Twins are all but certain to trigger. Especially since his teammates say Cruz has been as valuable in the clubhouse as in the lineup.

"He's one of those guys who makes you want to live up to his standards. He doesn't have to say much to make you want to work harder, to get better," Marwin Gonzalez said. "Guys like that can help turn a good team into a great one, because he sets such a professional tone. You expect more out of yourself."