After a tepid first half, the game sprung into life in the second period with Jordan Jones and Bailey Wright striking the bar in quick succession.
But Sunderland would be made to rue those missed chances when Tom Hopper put the Imps ahead, with Brennan Johnson then doubling the lead later in the second half.
It leaves the Black Cats with a major task on their hands at the Stadium of Light on Saturday as they bid to overturn a two-goal deficit in the second leg.
And head coach Lee Johnson will no doubt be targeting some major improvements following a disappointing display in all departments at Sincil Bank.
Our chief football writer Phil Smith has dished out his marks from the 2-0 defeat – and here’s how each player fared:
1. Lee Burge
Made a superb stop early on to deny Scully but will be left to rue his part in the second goal. A soft back pass gave Johnson the opportunity, and he charged down the clearance to score. 4 Photo: FRANK REID 2020
2. Luke O'Nien
Struggled to keep his composure in the second half. Threatened in moments as he broke forward but on the whole had little impact on the game. 5 Photo: FRANK REID 2020
3. Bailey Wright
Should have scored at the start of the second half when he had a free header inside the box. Uncertain defensively at times as Sunderland struggled with their distribution. 5 Photo: FRANK REID 2019
4. Tom Flanagan
Handed a tough task in his first start since the Papa John’s Trophy final. Started well defensively, but there were too many loose passes out from the back. Part of a defence that gifted away two soft goals. 4 Photo: Frank Reid