The Black Cats took an early lead when Ross Stewart was brought down by U’s defender Lloyd Jones, who was subsequently sent off.
Stewart then converted from the penalty spot before Elliot Embleton doubled the hosts’ advantage with a free-kick.
Cambridge pulled a goal back through Paul Digby, before Stewart added his second, while Nathan Broadhead and Danny Batth also got on the scoresheet.
Our chief SAFC writer Phil Smith has delivered his verdict on how each Black Cats player fared at the Stadium of Light:
. Anthony Patterson - 6
Little he could do about Digby’s effort as his team-mates switched off, and was otherwise a total bystander. Claimed set pieces well when required, though that was rare. 6 Photo: JPI Media
. Carl Winchester - 6
Started in a very unusual role on the left of a back three as a result of Dennis Cirkin’s absence. Left the pitch after ten minutes with what looked to be a muscle problem, which would be a major blow at such a key stage of the season. 6 Photo: JPI Media
. Bailey Wright - 8
Cambridge weren’t able to offer much through the game but that did owe much to the way Wright marshalled the dangerous Joe Ironside. Another strong display. 8 Photo: JPI Media
. Danny Batth - 7
Rarely troubled defensively but won his duels with ease and stooped to score a good goal in the second half. 7 Photo: JPI Media
1. Anthony Patterson - 6
Little he could do about Digby’s effort as his team-mates switched off, and was otherwise a total bystander. Claimed set pieces well when required, though that was rare. 6 Photo: JPI Media
2. Carl Winchester - 6
Started in a very unusual role on the left of a back three as a result of Dennis Cirkin’s absence. Left the pitch after ten minutes with what looked to be a muscle problem, which would be a major blow at such a key stage of the season. 6 Photo: JPI Media
3. Bailey Wright - 8
Cambridge weren’t able to offer much through the game but that did owe much to the way Wright marshalled the dangerous Joe Ironside. Another strong display. 8 Photo: JPI Media
4. Danny Batth - 7
Rarely troubled defensively but won his duels with ease and stooped to score a good goal in the second half. 7 Photo: JPI Media