(CNN)Manchester United was unceremoniously dumped out of England's League Cup competition by unfancied Derby County as new manager Frank Lampard upset his former boss Jose Mourinho to advance to the next round.
Jose Mourinho's Manchester United crisis deepens after Derby defeat
Tuesday's defeat in a competition now known as the Carabao Cup is the latest blow for United manager Mourinho this season with his team already trailing Premier League leaders Liverpool by eight points after six games. The defeat was also overshadowed by reports of more fractures in Mourinho's less than harmonious relationship with star player Paul Pogba.
Footage emerged Wednesday of the pair being involved in a training ground spat, with the French World Cup winner apparently not taking kindly to something his manager said.
"Mourinho is less to blame in this than Pogba," journalist Antony Kastrinakis told CNN World Sport as he reflected on their tense relationship. "It's clear."
A third-minute strike by United's Spanish maestro Juan Mata was canceled out by Derby's Harry Wilson -- on loan from the Red Devils' arch-rivals Liverpool -- just before the hour.
His Rams teammate Jack Marriott scored what looked to be an upset winner, until Marouane Fellaini saved manager Mourinho's blushes with a late injury-time header to make it 2-2 and force penalties.
Derby won the resulting, grueling shootout when, after 15 successful penalties, Derby's keeper Scott Carson saved Phil Jones' shot to send the holders out in the third round.
The Manchester team made wholesale changes -- including resting out-of-favor midfielder Pogba -- but couldn't outlast the gritty Midlands team.
In a pre-match interview, Mourinho said that he was resting key players Luke Shaw, Pogba, Victor Lindelof, Antonio Valencia and keeper David (De Gea).
"I gave a rest to these five players. I couldn't give much more. I had to play a very good team."
Despite a stellar World Cup -- in which he propelled France toward victory -- Pogba, who rejoined Manchester United for a then-record fee of £89 million ($117 million) in 2016, has not replicated his national team form for the Premier League club.
In widely reported comments, the Portuguese manager had told the 25-year-old midfielder that he is no longer United's "second captain," citing concerns about the Frenchman's attitude.
"The only truth is that I made the decision for him not to be second captain any more but there is no fallout, no problem," Mourinho said, according to the BBC.
"I am the manager. I can make these decisions."
In his program notes ahead of Tuesday's game, Mourinho said that he felt let down by some team members' attitudes.
"(Saturday's Premier League draw against Wolves was) an important lesson; a lesson that I repeat week after week after week, a lesson that some boys are not learning," he wrote, without specifically naming his most expensive signing.
"Every team that play Manchester United are playing the game of their lives, and we need to match that level of aggression, motivation and desire -- 95% isn't enough when others give 101%."
The East Midlands side appointed untested manager Lampard in May and since the beginning of the 2018-19 season he has led the Rams to sixth in the second-tier Championship with five wins, one draw and three losses.
The win at Old Trafford -- only his 12th competitive match -- saw him claim first honors against his erstwhile mentor and manager from his Chelsea days.
"I'm shell-shocked. To go down early at Old Trafford and play as well as they did was superb. I am a proud manager," Lampard said, according to the BBC.
"It was the easiest selection I have had. The players were superb against Brentford and they deserved the chance to play at Old Trafford.
"I wanted to bring a team who could really compete."
His opposite number, Mourinho, was dismissive of the competition which he had led his team to win last season.
"The Carabao Cup is not a worry any more - we don't play until next season. It is the minor competition we are involved in. We want to win and we are disappointed."
Elsewhere in the competition United's crosstown rival Manchester City continued its solid early-season run of form with an assured 3-0 win over Oxford United, with Gabriel Jesus, Riyad Mahrez and young English talent Phil Foden getting on the scoresheet, the latter with his first senior goal for the Light Blues.