Jason Kidd inspired his Dallas Mavericks to play elite-level defense in late December and most of January.

However, at the start of February, his inspiration appears to be petering out. In the last two games, Dallas is 0-2, with losses to the Orlando Magic and Oklahoma City Thunder. Two teams at the bottom of their respective conferences with 12 and 16 wins. And in those contests, Dallas allowed 54.4 points in the paint on average (25th in the league).

"That's one of the areas we've been struggling with," Kidd said after the loss to Oklahoma City.

What hasn't helped Dallas' defensive cause is missing rim protector Kristaps Porzingis. Since his bone bruise against Indiana on Friday, teams have a highway to the rim for easy layups.

Porzingis has transformed himself into one of the league's better defensive stoppers. He's averaging 1.7 blocks per game, and that number doesn't speak to the number of shots he affects at the rim on a game-to-game basis.

Blocked shots are nice highlights, but shots affected or deterred at the rim are where Kidd values Porzingis' defensive skillset.

"We don't always talk about blocked shots," Kidd said. "We talk about how we can change shots."

Without Porzingis changing shots, Dallas' outstanding defensive rating has also plummeted. What once was a top-five defensive rating team through January ranks 19th in the last two games with a rating of 115.6.

The ferociousness and tenacity on the defensive end slipped. And opponents are shooting 47 percent from the field and 35 percent from three against the Mavericks through the last three games. Stark signs of regression on the defensive end.

The reason why the defense is slipping

Part of the reason Dallas may not be defending as well as it was through late December and January is fatigue.

The NBA schedule is extremely long. Dallas played in two back-to-back contests in10 days. Fatigue isn't an excuse, but it could provide reasoning for recent struggles.

Another reason — and probably the more likely of the two — is without Porzingis, Dallas lacks the versatility it needs for Kidd's defensive schemes. Yet, in a way, this second explanation is the scariest of the two.

It means that the hope of the season rests on Porzingis' health — again. If history is any indication of where a circumstance like this one leads Dallas, things aren't exactly trending upward.

Porzingis is a monumental part of what Dallas does on defense. Without him, it's like driving a car without an engine. You won't get very far. Neither will Dallas if Porzingis' health isn't a guarantee.

His bone bruise still has him listed as day-to-day. Dallas' defense appears to be that way as well.

"We’re still positive," Jalen Brunson said after losing to Oklahoma City on Wednesday. "We know what we’re capable of and we just got to reset focus."

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Feature image via Jerome Miron-USA TODAY Sports.