CBS News is overhauling the weekday team at “The Early Show” in an effort to improve its long-standing third-place position in the network morning news ratings. Chris Wragge and Erica Hill, who have co-anchored the program’s Saturday edition since 2008, will replace Harry Smith and Maggie Rodriguez as weekday co-hosts beginning Jan. 3.

Marysol Castro, formerly of the weekend edition of ABC’s “Good Morning America,” will replace Dave Price as weather anchor. Jeff Glor, who has anchored CBS’s Saturday newscast, will join the weekday program as its regular news reader. Hill already appears on the weekday show as a news reader, while Wragge will leave his local news anchor position at CBS’s New York affiliate to take the national role.

CBS executives said they chose the new team for its energy and chemistry, pointing to Wragge and Hill’s ability to move between hard news and lighter stories on Saturdays. Executive producer David Friedman said the change was about finding the right team for the future, while CBS News President Sean McManus cautioned that he did not expect an immediate ratings turnaround.

The challenge is considerable. In the week before Thanksgiving, NBC’s leading “Today” averaged 5.6 million daily viewers, ABC’s “Good Morning America” drew 4.6 million, and “The Early Show” attracted 2.9 million, according to Nielsen. “Today” had not lost a week in nearly 15 years.

Smith, who has hosted CBS morning programs for 17 of the previous 25 years, will remain at the network as a reporter and primary substitute anchor for the “CBS Evening News,” “Face the Nation” and “Sunday Morning.” He expressed gratitude for his opportunities and wished the incoming team success. CBS said it was discussing future roles with Rodriguez and Price.

Television critic and Rowan University professor David Bianculli said a shake-up was understandable given the show’s persistent ratings struggles, though he found the abruptness of the changes surprising.