OXFORD United were stunned by 180 seconds of madness as they lost their Papa John’s Trophy opener at Cambridge United.

Former U’s striker Sam Smith scored twice at the end of the first half at the Abbey Stadium, with Luke McNally sent off for hauling down Harvey Knibbs in between.

Knibbs struck late in the Group H encounter and United will be frustrated the first three goals all came from corners, before 16-year-old Kai Yearn added a fourth in stoppage-time.

They did have Dan Agyei’s stunning long-range strike to cheer and there were some encouraging performances from several youngsters in a starting XI that showed 11 changes.

That line-up included a debut for Herbie Kane, who signed on loan from Barnsley yesterday.

He partnered Josh Johnson in the midfield two on the day the 16-year-old made his first start for the club, as did Tyler Goodrham – almost 22 months after his previous U’s appearance.

Joel Cooper and Michael Elechi were involved for the first time since last November, while Jack Stevens was the only senior player on a very young substitutes bench.

Cambridge made ten changes of their own and both sides took time to find a rhythm, but the hosts should have led after 16 minutes.

Their first corner was headed on to the top of the bar and fell to Mamadou Jobe a few yards out, only for Cooper to throw himself in front of the shot.

The game opened up and United enjoyed a threatening spell, with Goodrham and Cooper forcing Kai McKenzie-Lyle into identical saves away to his right with efforts from the edge of the penalty area.

Nathan Holland was finding plenty of space on the inside and shot just past the post, while Johnson and Kane were dropping deep to receive the ball and keep play moving.

It had been an encouraging half, until a former U’s player opened the scoring against Karl Robinson’s side for the second Tuesday in succession.

Smith’s goals were no Rob Dickie piledrivers, but the striker profited on a lapse in concentration to meet a corner at the near-post and head beyond Simon Eastwood.

Cambridge drove forward from the kick-off and Knibbs got the wrong side of McNally, who hauled the forward down – with referee Sam Allison quick to produce the red card.

It was already a horror end to the half, but it got even worse in the third minute of added time as Smith tucked home a flick-on as United again failed to defend a corner.

Clinton Nosakhare became the U’s second debutant of the evening at half-time, replacing Leon Chambers-Parillon.

He went into the back three alongside John Mousinho and Elechi, with Goodrham and Cooper as wing backs.

Neither player was in their natural position so it was no surprise Cambridge were quick to exploit the space down the flanks.

Smith almost had a hat-trick midway through the half when he twisted his body to fire into the ground, but United also looked to get forward whenever possible.

Gatlin O’Donkor replaced Holland and soon laid the ball into Elechi’s path, with the left back unlucky to strike the near post from 15 yards.

United were rewarded for their determination with 19 minutes left and it was an absolute beauty.

Agyei was 30 yards out and with opponents all around him when he took possession, but the forward made room for a shot and found the required curve and dip to beat McKenzie-Lyle.

The U’s enjoyed a brief spell of pressure, only for Cambridge to quickly restore their two-goal lead with another goal from a corner.

Simon Eastwood tipped over Liam Bennett’s long-range drive, but once again the hosts won the flick-on at the near post and Knibbs was on hand to tap home.

Josh Anifowose also made his debut, coming on for Kane late on, however he could not stem the tide. 

Cambridge spurned several chances late on as they broke through the U’s defence with ease, with Yearn eventually adding the fourth with an accomplished finish from 12 yards.

Cambridge United (4-4-2): McKenzie-Lyle, Bennett, Digby, Jobe, Dunk, Lanckester (Yearn 69), Weir, May, Worman, Knibbs, Smith (Brophy 77).

Unused subs: Mannion, Williams, O’Neil, Masterson, Beckett.

Booked: May

Oxford United (4-2-3-1): Eastwood, Chambers-Parillon (Nosakhare 46), McNally, Mousinho, Elechi, Kane (Anifowose 86), Johnson, Cooper, Goodrham, Holland (O’Donkor 60), Agyei.

Unused subs: Stevens, Watt, Smith.

Booked: Cooper, Johnson.

Sent off: McNally.

Referee: Sam Allison (Wiltshire).

Attendance: TBC.