Fa'atau jinked his way to within sight of the line before passing to Evans, who showed great strength to stay in-field near the corner flag as he twisted in Mark Jones' tackle to touch down.
Abdoulaye Faye, who only lasted 25 minutes before limping off with a twisted knee, was at the far post to meet one corner, after Dave Kitson had flicked on the initial delivery from Liam Lawrence.
Celtic's opener arrived in the 14th minute from the boot of Samaras after the former Man City striker picked up a long ball from Landry N'Guemo and twisted around the Motherwell defence to fire in a superb shot from 12 yards out into the top corner of the net.