The person spoke to The Associated Press on condition of anonymity because an official announcement had not been made by the team. The surprise move was first reported Thursday night by the soccer website FourFourTwo.com.
The 42-year-old Porter has been coach of the Timbers for the past five seasons, compiling a 60-50-52 record and guiding the team to the MLS Cup Championship in 2015. He was named the MLS Coach of the Year after his first season with the team in 2013.
Porter tied the Major League Soccer record league record for fewest losses through his first 100 games with just 25.