"I'm not confident", he said.
'It is hard for me to understand we finish second which I keep saying, that I won eight championships and three Premier Leagues but I keep feeling the second last season was one of my biggest achievements in the game'.
A man now on the books of MLS side D.C. United said: "I am sure Jose (Mourinho) has been getting the team right".
Last season's champions, Manchester City are the opposition for Unai Emery's first competitive match in charge of the Gunners.
He said that he believes Liverpool will finish ahead of Manchester United in second place and Tottenham Hotspur will finish fourth despite a summer in which Mauricio Pochettino's team did not spend a penny in the transfer market.
Those issues have provided an unwelcome backdrop to a hard pre-season, United's makeshift side having suffered defeats to Liverpool and Bayern Munich.
City's defence gets under way at Arsenal on Sunday and Guardiola confirmed he could select World Cup stars including Raheem Sterling and Kevin De Bruyne despite their lack of a pre-season.
Sergio Romero, Valencia, Marcos Rojo, Dalot, Ander Herrera and Matic are all injured for Leicester's visit, while Mourinho needs to check on the fitness of those that returned late from the World Cup.
"[Alexis is] more than ready but you can not have the players who arrived only last Monday after the World Cup semi-finals or final and three weeks' holiday".
Marcus Rashford, Victor Lindelof and Romelu Lukaku returned early and should be available. "They trained Monday, Tuesday, Wednesday and today, so you can imagine they are not really fit and ready". It is hard for me to understand we finish second.
Alisson, Fabinho, Naby Keita and Xherdan Shaqiri all arrived before the end of July, with Jurgen Klopp eager to work with his full squad throughout pre-season. 'When I listen, when I read, it's hard to believe we finished second because you are capable of making people who finish second (sound like we) were relegated. "I keep saying that I won eight championships and three Premier Leagues but I keep feeling that second last season was one of my biggest achievements in the game".
"It will be a hard season for everybody, not just for us".