Heigl, who played Izzie Stevens, made an exit from the show as she wanted to spend more time with her family and focus on her film career, reported Huffington Post.
"When Katie left, it was tough. You could understand why she wanted to go -- when you're offered USD 12 million a movie and you're only 26," Pompeo said.
"But Katie's problem is that she should not have renewed her contract. She re-upped, took a big raise and then tried to get off the show. And then her movie career did not take off," the 43-year-old actress added.
'Grey's Anatomy' is an American television medical drama that also stars "Made of Honor" actor Patrick Dempsey.
The show is currently showing its 10th season.