BBC Sport correspondent David Ornstein has revealed that Arsenal have failed with an opening bid to sign Celtic’s Kieran Tierney but remain optimistic of reaching a transfer agreement. The Gunners are keen to pursue a new left-sided defender this summer and Tierney has been earmarked as the prime choice to strengthen that position of the backline.

Writing on his official Twitter account, Ornstein confirmed that the Gunners have had £15m bid knocked back for the defender but they remain hopeful of sealing a transfer agreement with personal terms remaining a mere formality, he tweeted: “As reported elsewhere Arsenal have had an opening bid of £15m for Celtic left-back Kieran Tierney rejected - but there is optimism an agreement will be reached between the clubs, while personal terms for the 22-year-old Scotland international shouldn’t be a problem.”

The Gunners currently have Nacho Monreal and Sead Kolasinac competing for the left-back duties but both of them did not have the best of seasons last term. While Monreal has witnessed a genuine decline in terms of performance with age, Kolasinac has struggled to impress defensively despite being a force on the opposite end of the field.

As such, it makes perfect sense to pursue Tierney, who is balanced on both ends of the field while offering the Gunners with a potential long-term option. Should the Gunners finalise an agreement, they could sanction the sale of Monreal, who has been the subject of interest from Athletic Bilbao over the past few seasons.

The La Liga outfit have the unique policy of recruiting players from the Basque country and Monreal could come at an affordable price for them, given his Gunners contract expires at the end of the forthcoming campaign. The Spaniard has racked nearly 250 appearances during the past six-and-a-half seasons with the Gunners.