Manchester City manager Pep Guardiola concedes he failed to get the best out of Alexis Sanchez during the pair's solitary season together at Barcelona.
Guardiola's City host Sanchez's Arsenal in the Premier League on Sunday in a clash which could have significant ramifications in the title race.
The duo will be reunited after working together at Camp Nou in 2011-12, a campaign which saw Barca lift the UEFA Super Cup, Supercopa de Espana, Club World Cup and the Copa del Rey.
Despite that success, Guardiola admits his tactics did not necessarily suit Sanchez, whom he believes is benefiting from being selected as the central striker under Arsene Wenger.
"Alexis has played in Chile and in Italy with Udinese and played really well in Barcelona," Guardiola said of the Chile international, who has 14 goals in 22 matches across all competitions this season.
"It is normal when you play with Messi that people think that he is not at his level, as the highlight is always Leo.
"But Alexis helped us a lot and played well. I think the position that he is in now, as a striker, is perfect for him, it suits him perfectly.
"In Barcelona maybe I didn't help him too much as I like the wingers wide, and he can do that but he plays more between the lines closer to the goal.
"Some of the moments when he played as a striker, especially one game against Chelsea in the Champions League semi-final when we lost in London 1-0, he played as a striker in the second leg and we went 2-0 up.
"It was an unlucky game, we lost and Chelsea arrived in the final. He played there, so he is a player that can play in several positions: left, right, central. He is a fighter with character and spirit, and he is a winner.
"He is a class, class player but now I think he is playing really well. With Chile he has won two South American cups, that shows what a good player he is."