McCarthy -- who the 49ers interviewed in Mobile, Ala., during the Senior Bowl activities there -- had formally interviewed for the offensive coordinator positions with the Detroit Lions and Jacksonville Jaguars and was also being sought by Tennessee Titans coach Jeff Fisher. A member of Jim Haslett's staff in New Orleans since 2000, McCarthy was essentially a coaching free agent, with his Saints contract set to expire Feb. 15. The Saints, though, knew of his intentions to leave and granted him permission two weeks ago to interview with other teams.
It is believed that McCarthy, 41, highly regarded in NFL ranks and known for a scheme that relies on a power running game and vertical passing attack, was chosen by the 49ers over Cincinnati Bengals quarterbacks coach Ken Zampese. Securing him is a big step for Nolan, who continues to assemble his staff.
"We're going to use the system, the terminology, the principles that obviously started there in the glory days," McCarthy, who agreed to a three-year contract, told The Associated Press. "I always felt that it was the beauty of the West Coast system that it gave you great flexibility to operate in and out of personnel groups. Whether you want to change by design, injury or whatever the need is, you have great flexibility to do that."
The 49ers also hired George Warhop as their offensive line
coach, adding two more veteran NFL assistants to Nolan's new staff.
Haslett has now lost three members of his coaching staff since the end of the season. He fired running backs coach Dave Atkins two weeks ago, and quality control assistant Ben McAdoo left to accept an assistant coaching job at Stanford.
Since the Saints anticipated McCarthy's departure, they have been considering possible replacements, and it appears the candidates have been reduced to two: longtime NFL assistant Marc Trestman, who last season worked with the Miami Dolphins, and current Saints quarterbacks coach Mike Sheppard.
Trestman, who is also considering an offer to become offensive coordinator at North Carolina State, is believed to be the front-runner.
Although no official announcement has been made, the Saints have reached an agreement with Green Bay running backs coach Johnny Roland to assume the same position on the New Orleans staff. Roland, 61, is a longtime NFL assistant.
Under the guidance of McCarthy, a 12-year NFL veteran, the New Orleans offense was statistically ranked in the top of the league four times in five years and twice finished in the top 10.
"I plan on riding the high road out of (New Orleans), and Jim Haslett and I are very good friends," McCarthy told the AP. "We have an outstanding relationship. From an offensive standpoint, I think the Saints' best days are probably in front of them."
Len Pasquarelli is a senior NFL writer for ESPN.com. To check out Len's chat archive, click here.
Information from The Associated Press was used in this report.