Mavericks already have a glaring D'Angelo Russell problem on their hands

D'Angelo Russell is out of the rotation despite having a $6 million player option for next season, and this is awful news for Dallas.

Dallas Mavericks, D'Angelo Russell | Glenn James/GettyImagesThe Dallas Mavericks have found Kyrie Irving's replacement this season, as players like Ryan Nembhard and Brandon Williams have stepped up in the all-star's absence. The opposite, though, can be said of D'Angelo Russell, who has struggled to make do with the two-year, $11.7 million contract he signed this offseason.

Remember, Dallas signed the former Los Angeles Laker this past summer in hopes that he could make up for Irving's production. Dallas believed there was a chance Russell could replicate his…