There has been speculation about Pogba's Old Trafford future after he spoke of finding "a new challenge" in June, while his agent has said the France international wants to leave.
But pre-season has been going well for the squad, said Spaniard Mata.
"He's a fantastic midfielder and he's a very good guy," the 31-year-old added.
"I think he's happy."
Earlier in July, United manager Ole Gunnar Solskjaer also said Pogba has "never been a problem" and claimed there is an "agenda" against the player.
Mata wants 26-year-old Pogba's future to include helping the club to start lifting "big trophies" under Solskjaer, after two seasons without winning anything.
"Obviously as a team-mate, and as a friend also, I would like him to stay and to be happy because he is a very good player for us," the 31-year-old Spain international, who signed a two-year contract in June.
"We know we have to do better than last season. This club has won more trophies than any other club in England."
United have not won the Premier League since 2013, the year Sir Alex Ferguson retired, and their last major trophy was the Europa League in May 2017 under Jose Mourinho - three months after winning the Carabao Cup. Solskjaer is Mata's fifth manager at Old Trafford - an amazing statistic given the club prided itself on stability under Ferguson, who was manager for 26 and a half years. David Moyes was in charge when the midfielder joined United from Chelsea for a then club record £37.1m in January 2014 and he has since served under Ryan Giggs, Louis van Gaal, Mourinho and Solskjaer.
Sevilla were annoyed that Larouci played on when one of their players was down, but there can be no excuse for Gnagon's frustrated kick, which launched 18-year-old Larouci into the air and led to him being carried off on a stretcher.
"It is much too early in the season to create headlines by saying the things I think about the situation," Klopp said after the game, which Liverpool lost 2-1.
The German manager was watching his words, but midfielder James Milner described the challenge - for which Gnagon has apologised - as a "disgrace".
"Was it too much? I thought so, yes," Milner told LFCTV.
"We know it's only a friendly, but you don't see many red cards in friendlies, do you? You don't normally see too many tackles like that."
Sevilla midfielder Ever Banega could also have been sent off in the first half of a feisty friendly for catching Harry Wilson with an elbow.
Former Manchester City forward Nolito had curled Sevilla in front before Liverpool's Champions League hero Divock Origi thrilled a 35,654 crowd with an equaliser.
Liverpool fielded a whole new XI after the break, with the predictable impact on the flow of the game - but after Gnagon's dismissal, the Spanish side still found a late winner through substitute Alejandro Pozo.
On another brutally hot evening on the east coast of the United States - with temperatures at 34C at kick-off - Klopp ended a fiery first half by exchanging words with Sevilla's former Spain boss Julen Lopetegui. Banega had already gone in hard on at least one occasion when he brought the opening period to an end by flattening Wilson with the second of two swinging arms. He would surely have seen red as well on another night. There were more spiky challenges from both sides in a 15-minute spell at the end of the first half, before Gnagon swiped into the shins of Larouci, who later got on the team bus using crutches and with a brace on his leg. "It looks like Larouci was lucky but we have to wait. He hit him full throttle. Harry got a knock on his cheekbone and his eye so that was not too cool," Klopp added. "In general, I don't like overly hard games. The challenge is there to win the ball, that's the only reason. There are rules. I don't want to say anything specific about this game because there will be headlines. I want to have a holiday in Spain again."
Klopp said that there was no need for Sevilla to apologise, but after the game Gnagon did just that, calling his challenge "an odious act", while the La Liga side tweeted that they wish Larouci "a full and fast recovery". Lopetegui said "it was possibly a red card", adding that his 22-year-old French defender was "very worried because he knows it is a bad tackle and not a good decision". Klopp insisted he "hates losing", even in a friendly where he was still without his first-choice front three and goalkeeper, among "seven or eight" missing personnel. The European champions had started the game well, with right-back Trent Alexander-Arnold marking his first start of pre-season by creating a chance for Ben Woodburn, while Origi had an effort well saved by former Fulham keeper Sergio Rico. But Sevilla then grew into the game, with former Newcastle forward Luuk de Jong wasting two free headers before Jesus Navas found his former City team-mate Nolito to curl home.
The Blues are banned from signing players until the end of the next January transfer window, meaning that Christian Pulisic - signed from Borussia Dortmund for £58m in January and loaned back to them for the rest of last season - is the only fresh face in the squad.
That squad will be without the talents of Eden Hazard, following his move to Real Madrid.
Chelsea are able to call on many of the 41 players they loaned out last season, including Kurt Zouma, who went to Everton, Tammy Abraham, who won promotion with Aston Villa and Michy Batshuayi, who was at Crystal Palace.
So is there evidence that Chelsea-produced players can have an impact on the Premier League?
Chelsea finished third in the Premier League last season, 26 points behind champions Manchester City, but just six points ahead of sixth-placed Manchester United. Maurizio Sarri, Lampard's predecessor, won the Europa League, but struggled to meet the fans' demands when it came to home-grown talent. Callum Hudson-Odoi and Ruben Loftus-Cheek are two of the hottest prospects at Stamford Bridge, but the former was limited to just four league starts, while the latter made six. Andreas Christensen was the only other academy graduate to feature in the Premier League. However, Chelsea's promotion of youth was not the worst in the top flight. Among last season's final top six, the numbers show that the higher up the table a club finished, the fewer academy graduates they used.Chelsea will be expected to use more than three academy graduates next season, as Christensen remains at the club and Loftus-Cheek has signed a five-year deal, but Lampard will have to convince Hudson-Odoi his future is brightest at the Bridge, with Bayern Munich reportedly still interested in the 18-year-old.
Harry Kane's lob from the halfway line was a worthy winner as Spurs beat the Italian champions 3-2 in a thrilling encounter in Singapore.
What made Kane's outrageous finish even sweeter was that it was Wojciech Szczesny, a former Arsenal keeper, who was left scrambling as he realised the ball was flying over his head and into the net.
His goal capped an evening on which more than 50,000 fans at the National Stadium were treated to a showcase of world-class talent in this International Champions Cup match.
It even led to our reporter Simon Stone to say it could be "the best game I see all season - and we are only in July".
Juventus named a starting XI which included five-time Ballon d'Or winner Cristiano Ronaldo, alongside serial winners Leonardo Bonucci, Mario Mandzukic and Federico Bernardeschi. Gianluigi Buffon, 41, was back in goal for the Italian giants too, while new signings Matthijs de Ligt and Adrien Rabiot came on as second-half substitutes. And Tottenham didn't hold back either. As well as Kane, Son Heung-min, Lucas Moura and Dele Alli were all on show. There was also a first look at new record signing Tanguy Ndombele. A feast of talent. After a credit card was used instead of a coin in the pre-match toss, Spurs got the game under way with intensity and it paid off, as Erik Lamela gave them a half-time lead. But Gonzalo Higuain completed a terrific one-touch passing move to equalise, and then Ronaldo gave the fans in Singapore what they wanted with a thunderous finish.