The Gunners are currently the favourites to win the Premier League title this season, despite being third in the table heading into the final 12 games of the campaign.
Arsenal have not won the top-flight title since their famous unbeaten triumph in the 2003-04 season but have lifted the FA Cup for the last two years running.
Herrera and his Manchester United team-mates are preparing to welcome the north London side to Old Trafford for Sunday’s showdown in the Premier League.
And the Spaniard has been impressed by the improvement that he has seen from Arsene Wenger’s men in recent seasons.
Herrera is quoted as saying by Metro: “I think Arsenal, besides having many good footballers, they believe in themselves this season, both in the Premier League as in the Champions League.
“They’ve been winning cups and they are better now.”
United were 3-0 winners over Shrewsbury Town in the fifth round of the FA Cup on Monday night as they set up a quarter-final clash with West Ham United at Old Trafford.
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