Cruz, who signed with the Bears this offseason after he was released by the New York Giants, suffered a knee injury in Chicago's final preseason game on Thursday.
He thanked the city of Chicago in an Instagram post on Saturday.
Injuries derailed Cruz's career with the Giants, who released him on Feb. 13. They did not make an effort to re-negotiate his deal for a second straight season. He caught just 39 passes for 586 yards and a touchdown in 2016 after missing most of the previous two years with injuries.
Cruz is 2½ years removed from major knee surgery.
Cruz was a force for the Giants from 2011-14, a time span in which he caught 241 passes for 3,626 yards and 23 touchdowns. He also had a strong playoffs after the 2011 season when he had 21 receptions for 269 yards in four games and caught a touchdown pass in the Giants' 21-17 victory over the Patriots in Super Bowl XLVI.
He had signed a one-year, $2 million contract with the Bears. Only $500,000 of that was guaranteed.