The Eagles signed veteran quarterback Josh McCown to a 1-year contract to backup Carson Wentz, an NFL source said Saturday.

McCown, a 15-year veteran, had retired this offseason. His deal is worth $2 million fully guaranteed and could be worth up to $5.4 million if certain incentives are met. The Eagles were down two healthy quarterbacks after Nate Sudfeld (broken wrist) and Cody Kessler (concussion) suffered injuries in their first two preseason games.

Adding McCown gives the team a viable backup option at least until Sudfeld returns in about six weeks. While the Eagles have invested in Sudfeld’s growth the last three years, and he will likely reclaim his job, McCown’s experience and how he learns the offense could change the team’s mind.

The 40-year old McCown has 76 career NFL starts and a 23-53 record as a starter.

He will be playing in his 18th NFL season and will wear No. 18 with the Eagles. McCown was first selected in the third round of the 2002 draft by the Cardinals. He spent four seasons in Arizona before jumping out the league with six other teams – the Raiders, Panthers, Bears, Buccaneers, Browns and New York Jets.

He spent three seasons in Chicago (2011-13), the last two with Eagles receiver Alshon Jeffery.

While McCown’s signing doesn’t bode well for Kessler’s future with the Eagles, it also means that fifth-round rookie Clayton Thorson won’t likely make the 53-man roster. Unless something has changed with Sudfeld’s recovery, the team won’t keep four quarterbacks on the roster.

Thorson played much better in his second preseason game Thursday night against the Jaguars, so the Eagles may have trouble sneaking him onto their practice squad. But that would be the extent to which they could now keep him.