Joo Won spoke up on behalf of his "Yong Pal" co-star Kim Tae Hee at press conference for the drama. The press conference took place on August 20 in Seoul.

"Yong Pal" can be considered a success as the ratings for the medical drama continue to outpace those of any other weeknight drama. Ratings reached as high as 20.4 percent on August 11, making it one of the few dramas to earn such positive domestic ratings in 2015.

And yet Kim Tae Hee's acting in the role of the imprisoned heiress Han Yeo Jin has been the subject of criticism. She played an heiress in a medically induced coma for the first few episodes but once her character woke up the criticism began. It even prompted her agency, Lua Entertainment, to issue a statement to the Korean media outlet OSEN.

"Kim Tae Hee is trying hard to show a different side of herself than she did in the past. You can say that she is completely absorbed in her new character Han Yeo Jin. She's trying to let herself go and act as naturally as possible."

At the press conference Joo Won was asked how he felt about the criticism levied against his co-star. He defended her, saying that her acting was heartfelt and he did not understand why people were criticizing her.

"I can't judge Kim Tae Hee's acting but as a partner it was very upsetting to continue to hear things like that and I felt bad."

He went out of his way to comfort her.

"When critical articles about her came out I called her to comfort her. She was very worried about the fifth episode because the percentage might drop due to her fault."

The ratings did not drop. The fifth episode reached 18 percent and the sixth surpassed 20 percent.

"I told her she shouldn't worry. I told her the percentage would make her feel confident again. So I told her the result was because of her and it was all thanks to her efforts."

Both Joo Won and Kim Tae Hee were less than successful with their last dramas. His drama "Tomorrow Cantabile" reached 8.5 with the opening episode and then later dropped as low as 4.9 percent. It was one of his rare ratings failures. Kim's last drama did rate as high as 11.4 percent but she was criticized for her acting.

"She's just like any other actress; she works hard," said Joo Won in defense of his co-star. "There might be times when she's not perfect but the same goes for all the others. This is the first time I had criticism about my partner. It wasn't a good feeling."

What do you think about Kim Tae Won's performance in this drama?