Dirk Nowitzki defends Tony Romo

On the day the locked-out NBA was supposed to start training camp, Dirk Nowitzki decided to take on a difficult defensive assignment.

Nowitzki defended beleaguered Dallas Cowboys quarterback Tony Romo, who is being ripped after his three-interception performance keyed the biggest blown lead in franchise history during Sunday's 34-30 loss to the Detroit Lions.

"Dear tony romo. Don't worry abt all the critics," Nowitzki wrote on his Twitter account. "I heard that same garbage for a long time. Keep working hard and keep improving."

Nowitzki silenced the critics by leading the Dallas Mavericks to the NBA championship last season. It was sweet vindication for a superstar often stereotyped as soft. His team had blown a 2-0 lead in the NBA Finals five years earlier and made three first-round playoff exits in the next four seasons.

Nowitzki can relate to Romo being labeled as a choker despite statistics that offer evidence to the contrary.

The blame for the Mavs' previous playoff shortcomings often fell at the feet of their 7-foot superstar despite the fact that Nowitzki is one of only four players in NBA history with career postseason averages of at least 25 points and 10 rebounds per game. Nowitzki doesn't have to worry about that rap after fueling several stunning comebacks during the Mavs' championship run, including driving for a couple of game-winning layups in the NBA Finals against the Miami Heat despite a torn finger ligament and, in one case, a 101-degree fever.

Romo has the best fourth-quarter passer rating among active quarterbacks and has led 11 game-winning drives. That hasn't prevented the perception that he wilts in pressure situations from forming in the mind of many critics and fans, who use Romo's 1-3 playoff record and high-profile mistakes to support their theory.

It's particularly difficult to make the case for Romo as clutch after his turnovers were the key factors in establishing two unfortunate firsts in franchise history this season. The Cowboys had never lost after leading by 14 points or more in the fourth quarter until Romo's fumble and interception fueled a New York Jets comeback in the season opener. The Lions' rally from 24 points down Sunday set a record for the biggest blown lead in Cowboys history, as well as the biggest road comeback in NFL history.

And, to think, Nowitzki's critics used to say he couldn't defend.

Tim MacMahon covers the Cowboys and Mavericks for ESPNDallas.com.