Manchester United's Jose Mourinho appeared to criticise both Arsenal boss Arsene Wenger and ex-Red Devils manager Louis van Gaal in his first news conference since his appointment at Old Trafford.
Mourinho has had a fraught relationship with counterpart Wenger in the past, describing the Frenchman as a "specialist in failure" in 2014.
In the same year, the two coaches were involved in a shoving match as Arsenal lost 2-0 to Mourinho's side at the time, Chelsea.
Mourinho has won three Premier League titles with Chelsea, while Wenger lifted his third in 2004.
Speaking on Tuesday, Mourinho said: "Some managers -- the last time they won a title was 10 years ago. Some of them -- never. The last time I won a title was a year ago. So if I have a lot to prove, imagine the others.
"The reality is it was never important for me. I play against myself. I have to prove not to the others but to myself -- that's my nature. I would never be able to work without success.
"I have to always find the reasons why I have as many questions towards myself and the people working with me -- that's my nature. I could approach this job in a defensive point of view by saying 'the last three years the best we did was fourth and an FA Cup.'
"I could go into that side but I can't. Manchester United is a different dimension [to other clubs] but when person have the same menu year after year, it has to change for the better than worse.
"For United fans for many years, success was just routine -- but the last three years are years to forget. I don't want the players to start thinking we have to do better. To finish fourth is not the aim.
"This is what I do with myself. I am 53, not 63 or 73. I am a very young manager. If I have this approach of not trying to prove to myself or others, not go for big challenges -- then I'm in trouble. The reality is I was in trouble the past five months."
Van Gaal, who was sacked by United and replaced by Mourinho in May, came under scrutiny during his time at Old Trafford for the team's style of play and "philosophy."
United won the FA Cup under Van Gaal last campaign but failed to qualify for the Champions League following their fifth-place finish.
Asked about his aims for this season, Mourinho replied: "It depends on the way you want to face it. I was never very good playing with words and hiding behind words and hiding behind philosophies.
"I was never good with that. I never tried to be. I was almost much more aggressive in my approach with the risks that can bring.
"It would be easy, honest and pragmatic from my side to focus on the last three years and focus on the fact that we don't qualify for the Champions League and so on.
"It would be pragmatic to say let's work and try to get back to the top four and do well in Europa League. I'm not good on that -- I don't want to be, I want to be more aggressive. And to be more aggressive is to say we want to win.
"I can anticipate that any of you that come with a question about the style of play and what is before is the result ... I can imagine one of those questions is around the corner.
"I can anticipate by saying you can win a short competition, a couple of matches without playing well. But you can't win competitions by not playing well. What is playing well? To score more than your opponent; to make your fans proud because you win."