Djokovic slipped by seventh-seeded Tomas Berdych 3-6, 6-3, 7-6 (7-3), fighting off a Berdych match-point opportunity and then five of the first six points in the tiebreaker.
Berdych made a fifth-game break stand up for the first set only to have Djokovic jump out to a 3-0 lead before taking the second.
They traded breaks midway through the third set and Berdych, up 5-4, had a chance to end the match when Djokovic double-faulted, making the score 30-40. But Djokovic rallied by winning three of the next four points to force the tiebreaker.
He won four straight points in the tiebreaker for a 5-1 lead before putting the match away after 2 hours, 39 minutes.
Ferrer battled for nearly 2 hours before snapping a four-match losing streak to Murray.
Ferrer had a pair of first-set breaks, including one to complete a 14-point game and win the set. Murray twice took the lead in the second set with breaks but Ferrer answered both times and put the match away with a 12th-game break.
Second-seeded Rafael Nadal and fourth-ranked Roger Federer claimed Group B wins Sunday. They are to play their group match late Tuesday. If either wins in straight sets, he would secure a place in the semifinals. The other Group B match Tuesday sends Jo-Wilfried Tsonga against Mardy Fish.
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Michael Sam cut from the Dallas Cowboys