Upon moving to Manchester United last summer, some dared to question whether Zlatan Ibrahimovic was capable of continuing his astronomical goal scoring form at PSG in the Premier League.

28 goals and a number of ‘Zlatanesque’ quotes later, the critics have been silenced.

The big Swede has often carried United this season, and his goals have maintained the Red Devils’ push for a top four place and Europa League glory.

Yet despite these exploits, Zlatan is by no means guaranteed to stay in Manchester next season.

Jose Mourinho is keen to tie the striker to a new one year deal according to the Manchester Evening News, but Ibrahimovic appears to be keeping his options open until the end of the season.

A player of this ilk deserves to be playing in Europe’s premier competition at this stage in his career, and Zlatan is more than aware of this.

If United fail to tie the 35-year-old to a deal, they must replace the huge void sure to be left by the Swedish striker’s departure.

If Ibra does decide to move on, he will be flooded with offers from across the globe, but United must move fast to improve the squad in his absence.

Here is who they must sign this summer to improve the team in the wake of the potential loss of Ibrahimovic….

Romelu Lukaku

Romelu Lukaku is the logical straight swap for Ibrahimovic.

The Everton forward has been sensational this season, and leads the Premier League goalscoring charts with an impressive 24 strikes.

The Belgian striker has proven that he can consistently find the net in this division, with the Belgian already approaching 100 top flight goals since his debut in 2011.

Lukaku has proven to be deadly, yet reservations are still to be had over the big man. Originally brought Lukaku to English football by Chelsea, the forward failed to find the net while with the West London club.

Despite a prolific loan spell at West Brom, Lukaku was again shipped out on loan to Everton, before joining the Toffees in a £28 million deal.

The man to sell Lukaku from Chelsea? Jose Mourinho.

Questions have been raised as to whether the Portuguese boss would take a punt on Lukaku after paving the way for his exit at Chelsea, but the former Anderlecht youngster has a point to prove.

Whether United take a shot on Lukaku remains to be seen, and he’s going to cost. Yet the 23 year old could lead the United line for years to come, and can definitely become the man that replaces Zlatan Ibrahimovic.

Antoine Griezmann

Linked to United all season, Antoine Griezmann is exactly the type of world class player the Old Trafford side are looking to attract.

Voted as the third best player in the exclusive Ballon D’Or award ceremony, the French forward would drastically increase the quality in the Red Devils line up.

Close friends with Paul Pogba, the partnership the pair might forge could be nothing short of breathtaking.

Able to operate as a central striker or in a supporting role, the former Sociedad man finds space where others would not, and his ability to find the back of the net could prove the difference next season.

If a deal for Griezmann were to go through, United would be potentially looking at eclipsing the £89 million world record fee they parted with to acquire Pogba.

Griezmann has distanced himself from a Premier League move in recent months, but with Diego Simeone looking likely to depart the Vicente Calderon, the time for Griezmann to move on may by approaching.

Griezmann looks like a ‘United player’, and can achieve his dream of becoming the world’s best in English football.

Toni Kroos

Moving away from finding an Ibrahimovic replacement, United must address the middle of the park.

United want a team of world stars, and Toni Kross could be the latest addition to the squad.

After chasing David de Gea for years, Real Madrid are ready to finally secure their man, and will seemingly do whatever it takes to do so.

United have struggled to find a suitable custodian of this position for many seasons now, and should line up Kroos to fill the role.