Porter attended Indiana University where he played on the men’s soccer team from 1994 to 1997. He graduated in 1997 with a Bachelor's degree in sports management. In February 1998, the San Jose Clash selected Porter with the 3rd round (27th overall) in the 1998 MLS College Draft. He did not join the Clash until 1999 but his tenure there was short - he made just four appearances and, in his one start, was ejected in the 32nd minute. Following that performance, the Clash sent him on loan to the Sacramento Geckos of the A-League before waiving him in June. He quickly returned to MLS after being signed by the Tampa Bay Mutiny in July. He suffered from several knee injuries and had arthroscopic surgery on both knees during the off season before retiring on June 30, 2000. In 1997, Porter was a member of the U.S. soccer team which took the bronze medal at the 1997 World University Games.
On August 29, 2012, it was announced that he would become the head coach of MLS club Portland Timbers after the conclusion of the 2012 NCAA season.
Porter was named the 2013 MLS Coach of the Year after leading Portland to a 14-5-15 (57pts) record, finishing the regular season in first place in the Western Conference and with the third-best record in the league – just two points shy of MLS Supporters’ Shield-winners New York Red Bulls. In 2013, the Timbers set new single-season club marks in points, wins, goals (54), goal differential (+21), shutouts (15) and fewest goals allowed (33). Porter was awarded the 2013 Slats Gill Sportsperson of the Year Award from the Oregon Sports Awards.
Helping guide the Timbers to the MLS Western Conference Championship in two of the last three seasons, Porter has compiled one of the league's top winning percentages among active MLS head coaches (41W-25L-36D, .578) since 2013. The 25 career losses in his first 100 career games as an MLS head coach ranks tied for the fewest losses with San Jose’s Dominic Kinnear among all MLS coaches who have reached 100 or more games in the league. Under Porter’s guidance, the Timbers have made Providence Park one of the toughest places to play in the league, registering an impressive regular-season mark of 24-7-20 at Providence Park over the last three seasons (2013-15).
In 2015, the Timbers once again reached the MLS Cup Playoffs, setting a new single-season club record in wins (15), while leading the league with 13 shutouts. Since 2013, Porter has helped guide the Timbers to the fourth-most points among all MLS clubs (159), behind only the New York Red Bulls (169), Seattle Sounders FC (167) and LA Galaxy (165).
In 2000, Porter returned to Indiana University as an assistant soccer coach. After Ken Lolla left the University of Akron in December 2005, the Zips hired Porter as head soccer coach. After taking the Zips to two consecutive Mid-American Conference titles, and being named the 2007 MAC Coach of the Year, Porter signed a two-year contract extension in June 2008.
Following Akron's near-perfect season of 2009, Porter was rumored to be in talks with Major League Soccer club D.C. United about their vacant head coaching position. However, the University of Akron and Porter agreed on terms of a new contract, keeping him in Akron for the next five years.
Porter was named the head coach of the U.S. Under-23 Men’s National Team on October 20, 2011 while retaining his duties as coach of the Akron Zips. His first task was attempting to guide the U-23 team to a successful qualifying run in March 2012 for the 2012 Olympic Games in London; however, following a 2–0 loss to Canada and a 3–3 draw with El Salvador, the Americans were eliminated.
National champion Postseason invitational champion Conference regular season champion Conference regular season and conference tournament champion Division regular season champion Division regular season and conference tournament champion Conference tournament champion