Celtic are entering a key transfer window. With a change in manager often comes a heavy turnaround of players and reports have suggested that Brendan Rodgers could have up to £15m to spend.

With question marks over the depth of the Hoops' striking department, fans' dissatisfaction with the midfield's performance over the last year and some experienced squad members rumoured to be on their way out, the new manager has a task on his hand to rebuild the squad into a Champions League calibre outfit.

We've picked out FIVE transfers that we think could have a massive impact on the Celtic first team...

Steven Fletcher

Football - Sunderland v Newcastle United - Barclays Premier League - Stadium of Light - 5/4/15 Steven Fletcher celebrates after Jermain Defoe (not pictured) scored the first goal for Sunderland as Newcastle Tim Krul (L) looks dejected Reuters / Andrew Yates Livepic EDITORIAL USE ONLY. No use with unauthorized audio, video, data, fixture lists, club/league logos or "live" services. Online in-match use limited to 45 images, no video emulation. No use in betting, games or single club/leag

The Sunderland striker is on his way out of the Stadium of Light with his contract expiring this summer, which could finally trigger a Celtic move. He has been heavily linked with Celtic twice, back in 2009 before he left Hibernian and again in this year's January transfer window.

He's spent 2016 on loan at Marseille, chipping in with three goals and getting plenty of game time.

While not a prolific scorer in the mould of poacher Leigh Griffiths, the Scottish international could be a key foil for Griffiths at the tip of the Hoops' attack. He would certainly add depth to the position with Celtic lacking options in the event that 40 goal Griffiths becomes unavailable.

Mohamed Elyounoussi

Celtic fans know all about Mohamed Elyounoussi. He scored twice against the Hoops in this season's UEFA Europa League, both home and away, breaking green and white hearts.

The dynamic Molde attacker could be the man to revitalise a Celtic front four that has been frustrating to watch at times in the Scottish Premiership.

He was linked with the Hoops in the January transfer window in a reported £2m deal. That could be a bargain with the likes of Leicester City sniffing around the Norwegian international as a potential replacement for Riyad Mahrez.

Only 21 and with over 50 senior goals to his name already, this could be a player that the Bhoys rue missing out on if he moves elsewhere.

Kolbeinn Sigthorsson

Kolbeinn Sigthorsson is an experienced striker and could be a player that gives Celtic an edge in European competition.

The Icelandic international enjoyed five seasons in the Eredivisie with AZ Alkmaar and Ajax before heading to Nantes last summer. Things haven't been so rosy in France, but his scoring pedigree in seasons prior is enough to convince us he could make an impact at Celtic.

He was linked with a move to Glasgow in January for a reported £2.5m after falling out of favour at Nantes. That price could be a steal considering he's a key member of the Iceland squad heading to EURO 2016 - a side who finished above Netherlands and Turkey in qualifying.

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Ivan Mocinic

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With Stefan Johansen not reaching the heights of his Player Of The Year rated season of 2014/15 this time around and with captain Scott Brown not getting any younger, Celtic could do with some fresh blood in the heart of midfield.

Step forward Ivan Mocinic, a player who can add presence and leadership in the middle of the park. The 23 year old is captain of his club HNK Rijeka and made his debut for Croatia in November.

Celtic defender Jozo Simunovic seems to rate him. After speculation linking Mocinic to Celtic this season, compatriot Simunovic told reporters that the midfielder had all the qualities to be a success in Glasgow.

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Anthony Limbombe

Patrick Roberts has added much needed width to Celtic's attack in recent months but with Anthony Limbombe on the other side, the Bhoys could be an even more formidable outfit.

The 21 year old is a star attraction for Eredivisie side NEC Nijmegen and is reported to have been watched this season by scouts from Celtic, PSV, Manchester United and Borussia Dortmund.

Quick and direct, the winger could be a difference maker against packed defences in the Scottish Premiership. He knows how to find the net too, with 21 goals in two seasons.

Now could be the time to make a move before bigger clubs come calling.

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