For a decade and a half, nothing has been more dependable for the Dallas Mavericks than the historically sweet shooting touch of Dirk Nowitzki.

For the past month and a half, however, glimpses of the big German in a groove have been few and far between.

December was absolutely dreadful by Dirk standards. He shot 43.5 percent from the floor and a sickly 27.8 percent from 3-point range in 2014's final month, averaging 17.8 points per game. It was one of the worst shooting months in the career of a man who has scored more points than all but six players in NBA history.

January hasn’t been a whole lot better so far, even after he bumped up his numbers with a 25-point, 10-of-19 outing in Saturday’s blowout loss to the Los Angeles Clippers. In five games this month, Nowitzki is averaging 18.2 points, shooting 44.7 percent from the floor and 33.3 percent from the 3-point line.

“I pride myself on being an efficient scorer,” said Nowitzki, who has been fighting a mysterious stomach illness for weeks but reports that he seems to be shaking it. “I don’t think really since December I’ve been as efficient as I would like, but it’s about staying confident, working on your game. Just keep stepping into them when they’re there and eventually things will turn around.”

There is ample evidence to support that optimism.

These early-winter struggles actually continue a trend from recent years. That could be viewed as evidence of the toll Father Time has taken on Nowitzki’s 36-year-old body that is nearing the 50,000-minute mark in the NBA, including playoffs. It’s worth nothing, though, that the struggles have always coincided with some sort of conditioning issue, a category in which the stomach illness falls.

Nowitzki struggled in January 2013 -- averaging 16.9 points on 44.2 percent shooting from the floor, including 36.2 from 3-point range -- when he was early in his return from arthroscopic knee surgery that sidelined him for the first 27 games of that season. There was premature discussion that Dirk was done as a go-to threat at the time. He quieted that by shooting 50.5 percent from the floor and 43.3 percent from 3-point range after the All-Star break, numbers he’d be proud of at any point of his career.

January 2012, the first full month of that lockout-condensed season, was even uglier for Nowitzki: 15.1 points per game, 44.1 field goal percentage, 21.2 3-point percentage. Nowitzki, who admittedly was surprised when the lockout ended and wasn't in his typical shape when he reported to the abbreviated training camp, put up numbers near his career norms the rest of the season.

It’s not as if Nowitzki has been struggling to get good looks. The Mavs no longer rely on him to create his own shot very often, hardly ever running the isolation plays for him that used to be the bread and butter of the offense. They’ll still run the occasional post-up for him, particularly if he has a mismatch, but Nowitzki is primarily a pick-and-pop player and floor spacer at this point in his career.

Dallas’ flow offense continues to get Nowitzki, who is scheduled to welcome mentor Holger Geschwindner to town next month for the shot doctor’s annual midseason visit, plenty of looks he expects to knock down on a consistent basis.

“Every shot in the game has a little twist to it,” Nowitzki said. “Sometimes a guy pushes you, sometimes you’re open. You just have to react to what’s out there, but I still like to make the ones that I’m open. I’ve got to cash in on those, figuring that I’m not going to get a lot of wide-open looks in a game.

“I’ve got to be a little bit more consistent there and make some of the tough ones. It’s actually been weird. I think I’ve been making some of the tougher ones, and some of the open ones I’ve been rattling in and out.”

According to NBA.com’s data, Nowitzki has averaged 7.3 open shots per game since the start of December, as defined by no defender being within four feet when he lets it fly. He has made only 40.6 percent of those, including 13-of-44 (29.5 percent) from 3-point range.

The general reaction around the Mavs to Nowitzki’s slump: Just wait until the big German finds his groove again.

“Look, nobody’s going to have a great shooting night every night,” coach Rick Carlisle said. “You've got to get the looks, step into the shots and be aggressive. The results take care of themselves. I’m not concerned about that.”