On paper, Manchester United had a relatively successful summer transfer window.

The respective arrivals of Tom Heaton, Jadon Sancho, Raphael Varane and Cristiano Ronaldo mean that Ole Gunnar Solskjaer's squad looks far stronger than it did last season.

However, there are still some gaping holes in the squad that Solskjaer needs to address. During the summer, supporters were crying out for United to sign a holding midfielder, though no such move materialised.

Despite the improvements made to the squad in recent months, there's a growing sense that United may need to add more quality to their squad if they're to challenge for the Premier League title, and Fan Brands writer Omar Garrick has had his say on who United need to sign if they're to make their way back to the summit of English football...

1. Declan Rice

This is probably the most obvious target.

There are plenty of other midfield options out there, but it feels as though Declan Rice is the perfect midfielder for Solskjaer.

The 22-year-old is the right profile in terms of being young, driven and eager to win trophies. He's also a leader despite his career still being in its relative infancy.

The MEN reported in the summer that Rice was Solskjaer's number one midfielder target, but the club were priced out of a move by West Ham. However, their £100 million asking price is likely to drop the longer he goes without penning fresh terms in east London.

During Thursday's Europa League match in Croatia, Rice scored a fantastic solo goal as West Ham won 2-0 against Dinamo Zagreb, showcasing exactly what he could bring to the club.

United will likely have competition from Chelsea if they choose to reignite their interest in Rice, but they really can't afford not to lodge their interest once again.

2. Erling Haaland

Erling Haaland of Borussia Dortmund runs with the ball during the UEFA Champions League group C match between Besiktas and Borussia Dortmund at Vodafone Park on September 15, 2021 in Istanbul, Turkey.
Erling Haaland is going to be hot property next summer

With a release clause of €75 million, he's probably on everyone's wish list, but United definitely need to try and sign Erling Haaland next summer.

His goal record at Borussia Dortmund is ridiculous and it's no secret that Solskjaer is among his growing list of admirers.

Haaland has spoken of his admiration for Solskjaer in the past, and with Edinson Cavani not expected to extend his contract at Old Trafford beyond next summer, United need to make a move for the Norway international.

Of course, the youngster will have plenty of other potential suitors next summer, but signings like Ronaldo, Varane and Sancho prove United are still a huge draw.

3. Kieran Trippier

Kieran Trippier is a weird one. He seemed destined to sign for United this summer before Solskjaer opted to keep Diogo Dalot as Aaron Wan-Bissaka's deputy.

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I still think this move could happen because there's every chance Dalot could look to move on next summer if he isn't getting the game time needed for him to develop. However, even if Dalot does stay at the club, United should still make a move for Trippier.

United don't have the depth needed at right-back at the moment, and if you're going to challenge for the title then you need quality options in every position on the pitch.

It might sound like a tall order to sign all three of these players, but if United are serious about finally getting their hands back on the Premier League trophy then that might be what it takes.

Who do you think United should sign in the next transfer window? Follow our new United Fan Brands writer Omar Garrick on Twitter to get involved in the discussion and give us your thoughts on the matter in the comments section below.