Manchester City are looking to sign as many as four more players during the transfer window and want their business done by the start of the new season on September 12.
Nathan Ake completed a £41m transfer from Bournemouth on Wednesday evening.
Ake will join Ferran Torres at the Etihad Stadium after the Spain U21 winger joined from Valencia on Tuesday for an initial £20.8m fee, plus a number of add ons.
Defenders are now the priority, but deals for both a left-back and a second centre half, most likely Napoli's Kalidou Koulibaly, are still some way off.
Further up the pitch, City face the daunting task of finding long-term replacements for two Premier League legends in David Silva and Sergio Aguero.
Inter Milan's Lautaro Martinez remains the number one choice to fill the number 9 shirt, while The Athletic have reported City had enquired about the availability of Atletico Madrid's Joao Felix, who has endured a difficult start following his £113m move last year from Benfica.
The 25-year-old defender only returned from holiday on Tuesday and a day later was confirmed as Pep Guardiola's second summer signing.
Ake's move was a club-record sale for Bournemouth, and the defender said he is excited about playing under Guardiola.
"City have been the best side in England over the course of the last decade," he said.
"Coming here is a dream for me. This is a top side full of world-class players. Everywhere you look in this squad there are big names with international pedigree.
"Pep is a manager admired across the world - what he's done in the game speaks for itself. The success he's had is unbelievable and the style of football he plays really appeals to me".
Ake moved to Bournemouth from Chelsea for a club-record £20m deal in 2017 and was linked with a return to Stamford Bridge.
Chelsea had a buy-back clause on the Netherlands international but it is understood Frank Lampard was not interested in re-signing him.
Ake made 29 appearances for Bournemouth last season as they were relegated to the Championship, finishing a point from safety in 18th place.
Sky Sports' Adam Smith:
Of the current Premier League defenders aged 25 or under, only Hector Bellerin and Luke Shaw have racked up more top-flight appearances than Ake.
The chart below shows Ake's positional development, revealing a versatility which would appeal to Pep Guardiola, who moved defensive midfielder Fernandinho into central defence to cover Aymeric Laporte.
Since he made his permanent switch in 2017, the Cherries' win percentage jumps with him in the team and they concede fewer goals. That blend of youth, experience, versatility and effectiveness certainly bodes well for City.
For all the flowing, attacking football, Guardiola's side are shipping almost one goal per game - the same ratio as his inaugural season before the serious rebuild.
To put a figure on it: the defence is currently 34 per cent less efficient, compared with last season.
Much was made of how City failed to replace Vincent Kompany after his departure from the club, but it was the serious injury to Laporte which exposed the cracks.
Without Laporte, City's weaknesses were laid bare. Even with Laporte, a natural partner is missing.
Nicolas Otamendi, John Stones and Eric Garcia have been tested, but Guardiola has still preferred to play veteran midfielder Fernandinho as one of the pair. Fellow midfielder Rodri has played there, too.
The lessons are clear. City are scintillating in attack and have emerging stars in those areas to fill veteran voids, but needed to splash cash on at least one centre-back this summer.
City's defensive woes
Manchester City scored more goals than any other team for the third season running in the Premier League. Their total of 102 was 17 more than Liverpool but Guardiola's team struggled at the other end.
They had conceded 12 more goals than Liverpool at matchday 31 - when Liverpool finally won the title - although the Reds' subsequent drop-off allowed them to close the gap. City's 18-point deficit is clearly the result of weaknesses at the back.
Summer transfer window - key dates and times
The summer transfer window will run for 10 weeks from July 27 and close at 11pm on October 5.
A domestic-only window for trades between the Premier League and EFL then runs from October 5 and closes on Friday October 16 at 5pm. Follow all the news and analysis on Sky Sports News and across Sky Sports' digital platforms, including with our dedicated Transfer Centre blog.