Manchester United boss Jose Mourinho can appear to seek "war not football" during difficult periods, Barcelona legend Xavi has said in the Daily Mirror.
However, Xavi, who played for Barca during Mourinho's three-year reign at Real Madrid, said the Portuguese remains one of the finest coaches in the game and that his renewed rivalry with Pep Guardiola "can be the best in football."
The enmity between Barca and Madrid escalated during Mourinho's time at the Bernabeu and, speaking ahead of Wednesday's Manchester derby in the EFL Cup, Xavi said: "Sometimes, when things don't go well for Mourinho, he wants war not football -- like when he was at Madrid -- and I hope we don't see that again in England."
Xavi has already backed his former Barca boss Guardiola to change English football in his role as Manchester City boss and the 36-year-old midfielder, currently playing for Qatari club Al Sadd, said his battle with Mourinho is an added bonus for the country.
"When I knew they would be rival coaches again, I knew it would be good for football," Xavi said. "I knew it would be especially good for English football. They're two of the best coaches in the world and their duel can be the best in football."
United, though, are currently seventh in the Premier League table after Sunday's 4-0 loss at Chelsea and questions are being raised over Mourinho's management.
The Times reported on Tuesday that Mourinho has adopted a "hands-off and distant approach" in training. The newspaper, citing a source close to a senior United player, said Mourinho sometimes gave instructions at the start of sessions before heading to work at his desk, leaving assistant Rui Faria in charge. The paper added: "Mourinho's cold approach to his players in one-to-one situations has also disappointed some United players."
After beginning the season with four successive wins in all competitions, United are enduring a testing period. They lost 2-1 to Guardiola's City in the Premier League on Sept. 10 and have won only four of their nine games since, with two of those coming in the Europa League and one in the EFL Cup.
The EFL Cup victory over Northampton Town set up Wednesday's fourth-round meeting with City, and Xavi expects Mourinho -- who won the League Cup three times with Chelsea -- to take the competition seriously.
"The domestic competitions have to be everything for United and Mourinho this season," he said. "I don't think this season they can win the Premier League. These competitions are their hope for a trophy.
"Once Mourinho has had another transfer window, maybe they'll be ready, but for now they must secure a finish in a Champions League spot -- that's where United belong."
City are also in the midst of a difficult period, with Guardiola's side on a five-game run without a win after 10 successive victories at the start of his tenure, although they remain top of the Premier League on goal difference.
"Pep will also want to win his first competition with City," Xavi said. "That will be important for him.
"Even with City dropping some points in the league, I still think under Pep they'll be champions this season."