Second-half strikes from David Ajiboye and Joel Randall saw the Imps defeated by Peterborough United at the Weston Homes Stadium.
City had the first sight of goal in the contest when a half-cleared corner fell to Jack Burroughs, but he volleyed over the crossbar.
Hector Kyprianou then headed wide of the target as Posh started to gain momentum.
The home side came even closer when Jonson Clarke-Harris forced Lukas Jensen into a decent save at his near post.
The Imps were managing to frustrate their hosts however and almost went ahead when Adam Jackson connected with a corner, but his header floated wide.
A couple of minutes later Ethan Hamilton carved the Peterborough defence open with a perfectly weighted through ball.
Danny Mandroiu took the pass into his path, drawing Nicholas Bilokapic out of his goal, but his dinked effort rebounded off the crossbar.
In the 41st minute Sean Roughan found himself unmarked at the back post, but he headed over when the ball bounced through to him.
Just after the break Posh nearly broke the deadlock, with David Ajiboye whipping a ball across the face of goal, but Mason-Clark struck wide at the back post.
Ajiboye then tried his luck on goal as a headed clearance fell to him on the edge of the box, but Jensen made a great save to deny him.
The substitute wouldn’t be denied in the 52nd minute however as a quick counter-attack resulted in the winger arrowing a shot into the top corner.
City worked hard to provide a response, and Hakeeb Adelakun had an opportunity after Jensen’s goal kick left him with space in the box, but his shot went wide.
After 68 minutes Peter Kioso found some space in behind the Imps’ defence and forced Jensen into another good save.
As City went in search of an equaliser Posh started to find more space and Ajiboye went close again as he showed good feet in the box, but this time his shot was too high.
Peterborough doubled their lead with six minutes to go as Mason-Clark’s ball into the box deflected into the path of Joel Randall who finished past Jensen.
Harrison Burrows came close to adding a third in injury time but his effort cannoned off the crossbar.
Peterborough: Nicholas Bilokapic, Harrison Burrows, Ronnie Edwards, Josh Knight, Jonson Clarke-Harris, Ephron Mason-Clark (Ryan De Havilland 88’), Kwame Poku (David Ajiboye 43’), Joel Randall (Ricky-Jade Jones 88’), Hector Kyprianou, Archie Collins, Peter Kioso.
Goals: Ajiboye (52), Randall (84).
Imps: Lukas Jensen, Alex Mitchell (Dylan Duffy 84’), Adam Jackson, Paudie O’Connor, Jack Burroughs, Sean Roughan (Jaden Brown 71’), Ethan Erhahon, Ethan Hamilton, Reeco Hackett, Daniel Mandroiu (Olamide Shodipo 68’), Hakeeb Adelakun (Ted Bishop 68’).
Referee: Sunny Singh Gill.
