The Royals made a significant move to strengthen their pitching rotation on Thursday by signing free-agent left-hander Jason Vargas.

Vargas, with the Los Angeles Angels last season, was signed to a four-year, $32 million contract by Kansas City. He earned $8.5 million last season.

To make room on the 40-man roster, the Royals designated backup catcher George Kottaras for assignment. He batted .180 in 46 games this year.

The long-term commitment, Vargas said, came because he liked Kauffman Stadium, the friendly Kansas City fans and the recent improvement made by the team.

"What excites me about the team is how I've seen the team grow and progress a lot over the last four or five years," he said. "You know what they put out there is a great team, and their defense is spectacular. I just hope I can be a piece of the puzzle that helps move us forward."

Four years is also beyond the length that general manager Dayton Moore previously indicated he's comfortable giving to veteran players, but he said, "I think the most important thing is that our medical team felt very comfortable, our scouting judgment was very sound with the length of the contract as well. It all kind of lined up together."

The Royals faced the loss of two starting pitchers when right-hander Ervin Santana and left-hander Bruce Chen entered the free-agent market. That left only right-handers James Shields and Jeremy Guthrie as sure-fire starters for 2014. So Vargas, an eight-year veteran, provides needed experience that would be lost if Santana and Chen sign elsewhere. Santana probably priced himself out of the Royals' reach with reported expectations of a five-year deal at $100 million or more.

In fact, asked about Santana, Moore said: "It's probably a difficult maneuver for us at this point in time, but we'll stay engaged and see how that unfolds."

However, Moore did not rule out Chen's possible return. He also indicated the club is open to signing another starting pitcher.

As the roster now stands, others in the hunt for rotation jobs likely will include left-handers Danny Duffy and Will Smith and right-handers Wade Davis, Yordano Ventura and Kyle Zimmer. Luke Hochevar, who spent last season in the bullpen, is another possibility. Luis Mendoza dropped out of the picture when he signed to pitch in Japan.