This is no ordinary January transfer window for Manchester City, but then this is no ordinary season for manager Pep Guardiola.

His team -- winners of the past four Premier League titles -- are 12 points adrift of leaders Liverpool in this season's race, with fixtures against Arsenal, Newcastle, Liverpool and Tottenham all to come in February.

Participants in two of the past four UEFA Champions League finals, City's hopes of continuing in this season's competition rest on the result of their make-or-break game against Club Brugge at the Etihad Stadium on Wednesday. Win, and they carry on. Lose, and it's an early exit from European competition for the first time since 2012-13.

In response to what has been a difficult start to the campaign, City are trying to regenerate.

While battling to save their season, striker Erling Haaland has been signed to an unprecedented 9-year contract, and 130 million has been committed to sign three new players -- Omar Marmoush (60m, Eintract Frankfurt), Abdukodir Khusanov (40m, Lens) and Vitor Reis (30m, Palmeiras) -- in the January window so far. And there is the prospect of more to come before the deadline on Feb. 3.

It's a different approach for City, who haven't made a significant January signing since bringing in Aymeric Laporte for 57m from Athletic Club in 2018.

City's shift in thinking about transfers

Man City have been forced into action in part because of the injuries that have decimated the start to their season. But there's also an acceptance that changes to the squad should have been made last summer. Instead, after winning a record fourth consecutive top-flight title, Guardiola decided to stick with the players he knew and trusted.

Savinho, the 20-year-old winger, was brought in for 30m from City Football Group members Troyes, after impressing on loan at Girona, another of City's sister clubs in LaLiga. That would have been the sum total of the incomings had Ilkay Gündogan not unexpectedly become available on a free transfer from Barcelona, just a year after leaving City to move to Camp Nou. Five months on, and Guardiola has already admitted it was a mistake not to do more to refresh the squad when he had the chance. Amid struggles in the Premier League and the Champions League, he has paid the price.

"In the summer, the club thought about it and I said, 'No, I don't want to make any signings,'" he said in a news conference before the 2-2 draw at Brentford. "I relied a lot on these guys and thought I could do it again. But after the injuries -- wow -- maybe we should have done it."

The season-ending knee injury to Ballon d'Or winner Rodri in September has been the most damaging, but other key players have faced issues, including Rúben Dias, John Stones, Mateo Kovacic, Nathan Aké, Manuel Akanji, and Kevin De Bruyne. The problems in defence have been so severe that 19-year-old Jahmai Simpson-Pusey has had to start games in the Premier League and Champions League, while midfielder Matheus Nunes has been used as an emergency right-back.

"Last season we didn't do much, due to the exceptional quality of the team," Guardiola said last week. "We anticipated three or four [signings] and we should do it in summer. We had to do it here [in January] for the amount of injuries, the problems that we had."

Injuries to defenders have had a major impact on City's January transfer business. Sources have told ESPN that 20-year-old Khusanov and 19-year-old Reis were pencilled in as targets for next summer. But they've been fast-tracked to the Etihad six months ahead of schedule to guard against more problems at the back in the second half of the season.

There are questions over the durability of Stones and Ake after numerous injury problems, while captain Kyle Walker joined Milan on loan after expressing his desire to move on. In the case of Reis, who has made only 22 senior appearances for Palmeiras, City agreed to pay more (around 30m) to bring him to the club now. Palmeiras' original plan was to keep him until the summer and have him available for the FIFA Club World Cup.

Both Khusanov and Reis are predominantly centre-backs, but might find they're used at right-back -- at least for the rest of the season. Josko Gvardiol, another young defender signed by City, arrived from RB Leipzig for 77m in 2023 as a centre-back, but has been used more frequently as a left-back.

Continuing injury problems meant Khusanov had to be thrown straight in from the start against Chelsea on Saturday. In a disastrous first five minutes, he gave a goal away, misplaced a number of passes and was booked for chopping down Cole Palmer. It was a tough introduction, in part because the Uzbekistan international had only a handful of training sessions with his teammates before his debut. It was made more difficult by the fact that he doesn't yet speak English and January signings don't get the same bedding period that benefits summer arrivals.

Why City moved for Marmoush despite risks

There is hope that Marmoush -- older and more experienced -- is better placed to make an immediate impact.

Sent on loan to the second tier of German football as recently as 2021, the Egypt international shot to prominence after scoring 37 goals and providing 20 assists from 67 games over a successful 18 months at Frankfurt following his free transfer from Wolfsburg in 2023. Signing Marmoush for around 60m is considered a risk by some at City, despite his fantastic start to the season with Frankfurt, but one they are willing to take.

City began the window with little hope that Frankfurt would entertain offers for him while they were so well-placed in the Bundesliga (they're third after 19 games) and in the Europa League (they're second with one round of games left to go in the group stage). Frankfurt knocked back an opening offer of around 50m to sign the 25-year-old, but after negotiations in mid-January, a fee of more than 60m plus add-ons was agreed.

According to sources, Man City's stance is that they had hoped winger Oscar Bobb could fill the void left by Julián Álvarez (who left in an 81m deal to join Atletico Madrid) in the summer only for the Norway international to suffer a broken leg on the eve of the Premier League season. It was unfortunate timing given how well Bobb had performed during preseason.

City have struggled defensively this season but have also struggled for goals. Before Phil Foden's recent burst of form, their second top scorer this season behind Haaland was Gvardiol, a defender. The hope is that Marmoush can chip in with goals in a similar manner to Álvarez, who averaged one every three games before he joined Atletico.

The Álvarez deal largely helped City fund their January signings, as it handed City a profit of around 65m on the modest fee 15m they paid River Plate in 2022.

On top of that, the club agreed fees to move on academy graduates -- counted as pure profit on the books in terms of Profit and Sustainability (PSR) rules -- which could total 276m in the past five years alone; including Taylor Harwood-Bellis (20m, Southampton), Liam Delap (15m, Ipswich Town), and Cole Palmer (42.5m, Chelsea). It means that while other clubs are battling to stay on the right side of PSR, City are able to spend freely while digging themselves out of a hole.

There's a chance there will be more to come before the deadline, too, with the club actively looking at central midfielders. They would be interested in former City player Douglas Luiz if he's allowed to leave Juventus this month; Éderson at Atalanta is another option, although a deal in the summer is considered more likely. The same goes for Juventus full-back Andrea Cambiaso.

Like January, the summer window is likely to be another busy one for City. Among other things, the club are watching closely what happens with Joshua Kimmich and Jamal Musiala as they approach the end of their contracts at Bayern Munich and sources have suggested there could be some big deals on the horizon.

City have used January to try to save their ailing season; Guardiola will hope they've also taken the first steps towards building his next formidable team.