Nine-time Pro Bowl left tackle Walter Jones has left Seahawks practice early with an apparent back injury.

The 35-year-old linchpin to Seattle's offensive line for the past decade was practicing Monday for the third time since training camp began July 31. He took part in one series with the starting offense when he left the field in pain.

He stood and kneeled next to a trainer while wincing and holding his back for a few moments. He eventually summoned the trainer to escort him into team headquarters.

Jones has missed time in Seahawks training camp before because of contract issues.

But this time he is coming off microfracture knee surgery and is learning the new zone-blocking scheme of first-year offensive coordinator Greg Knapp.