Aguero called time on his decade-long stay at City recently and will join Barcelona on a two-year deal when his Eithad contract expires at the end of next month, leaving a vacancy in Pep Guardiola’s squad.
City are one of several clubs monitoring Harry Kane, who has expressed a desire to seek a new challenge away from Tottenham Hotspur, though chairman Daniel Levy is reluctant to sell.
Speaking in annual end-of-season interview with City’s in-house media, Al Mubarak said that the Premier League champions will not stand still in the summer transfer market and stressed the importance of signing new talent.
Though he expressed faith in the squad which reached City’s first-ever Champions League final, losing 1-0 to Chelsea in Porto on Saturday, he insisted that reinforcements will be added in “a couple of key positions”.
“One of the things I’ve learned over the years is you need to constantly bring talent into the team, refresh, and particularly when you are at a high level, when you are on the top,” he said.
“Having won the league, it is not the time to actually sit back and be content. That actually would be your biggest mistake. This is the time to send a strong message that there’s no contentment, that you’re not satisfied with just winning the league.
The City chairman added: “We lose a very important legend in Sergio Aguero, very hard shoes to fill, but I’m confident that we will we will find the right player to fill those shoes.
“There are other areas within the group, within the team that obviously need investment. Not too many. It’s not about numbers, it’s about the quality.
“I think the squad is a phenomenal squad. You don’t win the Premier League and you don’t reach the Champions League final if you don’t have an incredible squad and we have that. We will bring quality into the squad in a couple of key positions.”
Aguero scored 260 goals in 390 appearances for City and is fourth on the Premier League’s all-time list of goalscorers with 184. Kane is just 18 goals behind Aguero’s total at the age of 27.