Ryan Tannehill ruled out against Steelers with knee sprain

— -- Miami Dolphins quarterback Ryan Tannehill has been ruled out of Sunday's playoff game at Pittsburgh, sources told ESPN.

With Tannehill out, backup Matt Moore will start for the fourth week in a row.

The Dolphins apparently determined Tannehill isn't ready to return from a sprained left knee he suffered in Week 14.

Moore, a 10th-year pro, is 2-1 as Tannehill's replacement and will make his first career postseason start. Moore has eight touchdown passes, three interceptions and a quarterback rating of 105.6, which is higher than Tannehill's career-best 93.5 this year.

Tannehill hadn't missed a game in five NFL seasons until he was sidelined against the Arizona Cardinals. He has never played in the postseason, and the playoff game will be Miami's first since 2008.

ESPN's James Walker and Adam Schefter and The Associated Press contributed to this report.