Celtic have already completed their first signing of the summer transfer window, which opened for business on Sunday, by agreeing to bring Kieran Tierney back to Parkhead.
The Scotland international will officially return to the club at the end of this month, upon the expiry of his contract at Arsenal, to be Brendan Rodgers’ left-back for the 2025/26 campaign and beyond.
Tierney, as you can see in the graphic above, won five Scottish Premiership titles during his first stint in Paradise after coming up through the academy system, before being sold to Arsenal for £25m in the summer of 2019.
Six years later and the Scottish full-back is returning to the club on a free transfer to bolster the Northern Irish head coach’s options at the back next term.
Tierney is not the only former Celtic full-back sold for big money who is on the move this summer, though, as Jeremie Frimpong has signed for Liverpool from Bayer Leverkusen for a reported fee of £29.5m.
How Celtic hit the jackpot with Jeremie Frimpong
The Hoops hit the jackpot with the full-back when they snapped him up from Premier League giants Manchester City for a very modest fee of £300k in the summer of 2019, a few months after Rodgers left to join Leicester City.
Celtic were willing to take a gamble on a player who had not played a minute of senior football up to that point, as he had been playing
U23 and U18 football for City.
Because of his lack of senior experience, there was no way for the club to know how he would adapt to playing regular first-team football in Scotland, which is why it was a risk to bring him in as a right-back option.
However, he hit the ground running for the Hoops, winning the domestic treble in the 2019/20 campaign, with a fantastic debut season as a senior player.
Frimpong stayed at Celtic for another six months, playing 22 times in the 2020/21 Premiership season, before signing for Bayer Leverkusen in a deal worth up to £11.5m at the start of 2021.
This shows that the club hit the jackpot with the defender because they were willing to take a gamble on an inexperienced young full-back from England for a modest fee, and went on to make a huge profit on the defender.
Frimpong then went on to provide 30 goals and 44 assists in 194 appearances for Leverkusen in all competitions before his big-money move to Liverpool this summer.
The Scottish giants are now reportedly eyeing up a move for the full-back who could follow in the Netherlands international’s footsteps at Parkhead.
Celtic eyeing move for English full-back
According to The Scottish Sun, Celtic are one of the teams interested in a deal to sign left-back Harley Mills from English League One side Peterborough United in the summer transfer window.
The report claims that the Posh are currently mulling over an approach from Premier League side Fulham, who have offered £1m for the teenage defender, which shows that there is competition for his signature.
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It states that Celtic have joined the race for the League One full-back because Rodgers wants to bring in competition in the left-back position for Tierney, who is poised to return to Parkhead on a free transfer from Arsenal at the end of the month.
Greg Taylor is out of contract and currently due to move on from the Scottish giants this summer, whilst Jeffrey Schlupp’s loan deal has expired, which has left Tierney as the only left-back contracted to the Hoops heading into next season.
Mills has been identified as a player who could come in to provide back-up in that position initially, as a replacement for Taylor, and he could now come through the door this summer as Frimpong 2.0 if Rodgers signs him.
Why Celtic should sign Harley Mills
Firstly, it is worth reinforcing that the 19-year-old talent would only be a second-choice at left-back in the 2025/26 campaign to start with, because Tierney will be the go-to option given what he achieved in his first spell at Parkhead.
This means that there will not be a lot of pressure on Mills to perform straight away, as was the case when Frimpong arrived from Manchester City’s academy, and that is backed up by a potential fee of £1m, which is not a mind-blowing amount of money to spend on a squad option.
He would, therefore, be given time to adapt and adjust to senior football in Scotland, as the young left-back does not have a wealth of experience as a first-team player under his belt.
Mills, who was hailed as “outstanding” by youth coach Jamal Campbell-Ryce, has played 20 times for Peterborough, including 12 appearances in League One, but did catch the eye at Wembley in the final of the EFL Trophy.
The English star scored a phenomenal free-kick in a 2-0 win over Birmingham City for his side, and that capped off what was an excellent campaign for the Posh academy graduate in that competition.
Appearances
6
Sofascore rating
7.25
Goals
2
Key passes per game
1.2
Big chances created
1
Tackles + interceptions per game
3.2
Duel success rate
67%
As you can see in the table above, Mills showcased his quality in and out of possession across six appearances in the EFL Trophy, winning the majority of his duels with opposition attackers whilst also scoring two goals and creating one ‘big chance’ for his teammates.
He only started eight games in League One, averaging 3.2 tackles and interceptions per game and winning 62% of his duels, but his form in that cup competition shows the kind of potential he has as a left-back.
Mills has shown potential as a strong defender, who can win his duels at an efficient rate, and as an attacking force with his quality as a scorer and a creator of goals, which suggests that he is worth gambling on for a fee of £1m.
Like Frimpong, he could be a low-risk full-back signing from English football who could go on to be worth millions more in the future if things go well for him in Glasgow.
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