Tierney was considered as a top target for the Magpies earlier this summer, and it was anticipated that a proposal could be made.

However, the Tyneside outfit have decided to sign Hall instead. The 18-year-old will join them on loan with a mandatory buy clause.

Eddie Howe 's side have agreed a package of £35 million for the youngster and he is expected to be a regular starter for the club.

Meanwhile, Tierney could yet leave the Gunners. The north London giants prefer a permanent sale or a loan deal with a buy obligation.

Real Sociedad have expressed an interest in signing the Scot, but the Gunners have turned down their season-long loan proposal.

Tierney was not in the matchday squad for the season opener against Nottingham Forest , but could be available on Monday night.

Gunners boss Mikel Arteta recently said that Tierney remains a key player in the club, having featured in the Community Shield.

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