Actress Katie Holmes filed for divorce from Cruise in June (12), while the Top Gun star was in Iceland wrapping new thriller Oblivion, and she subsequently won primary custody of their six-year-old daughter Suri.
The 50 year old has put on a brave face in the wake of his family break-down and continued his shooting schedule for All You Need Is Kill in London, thousands of miles away from his child.
And now McQuarrie, who worked with Cruise on both Mission: Impossible - Ghost Protocol and Valkyrie, has spoken out to commend the actor for staying committed to his work during the upheaval in his personal life.
He tells People magazine, "There's a commitment (to his movies) that is huge while all this enormous change is happening in his personal life. You can't simply put a movie on hold and go off and deal with your personal issues.
"He was finishing (Oblivion) when he learned his wife was divorcing him. He was immediately committed to (All You Need Is Kill) and there was no way he could not honour that commitment. You are talking millions of dollars, hundreds of jobs.
"His hands have been tied... I can tell you that I haven't had a meeting with Tom that was not interrupted by a phone call with his daughter. His heart is broken. His misses his little girl and works very hard at parenting."