Celtics and Thunder lay down markers in series openers

The Cold Wire

Kendrick Perkins Makes A Guarantee About Oklahoma City Thunder

(Photo by Jamie Squire/Getty Images)   After sweeping the eighth-seeded New Orleans Pelicans in the first round, and predictably so, Shai Gilgeous-Alexander and company headed into the second round against a much tougher opponent in the Dallas Mavericks, led by Luka Doncic and Kyrie Irving. Although the Thunder were still thought to have a great chance to advance to the Western Conference Finals, the Mavericks were expected to pose a tougher thr…