That is the opinion of Gunners legend David Seaman.
Emery has taken on the tricky challenge of revamping his squad with a reported budget of £45m this summer.
Having missed out on Belgium winger Yannick Carrasco, the Arsenal manager is currently targeting Celtic left-back Kieran Tierney and Crystal Palace forward Wilfried Zaha.
With a busy schedule expected this term thanks to Carabao Cup, Europa League and FA Cup duties added on to the Premier League, Emery will need as much strength in depth as possible.
“I really think they should be looking to sign Tierney before setting their sights on Zaha”
Moreover, the Gunners conceded 51 Premier League goals last season, the ninth-best defensive record in the competition.
And ex-Arsenal and England goalkeeper Seaman has outlined exactly why Tierney should be made a priority over Zaha, calling into question Emery’s seemingly shaky backline.
“Yes, Zaha is a good player who could do well for the club, and yes I know I would say as a former goalkeeper that the defence is the first place to look at in terms of signing new players – but the simple fact is that the backline needs strengthening,” Seaman told Football London.
“It’s no secret that Arsenal need to strengthen their defence, certainly after missing out on Champions League qualification. I think Tierney would be an ideal addition for Arsenal.
“He’s young, he’s talented. I think I’m right in saying he’s already captained his club and country and by all accounts he’s a hard worker with a great attitude.
“Being British he’d also settle in straight away and there would be no period of adjustment. I really think they should be looking to sign Tierney before setting their sights on Zaha.”
Arsenal saw a £15m bid for Tierney rejected last month, with Celtic boss Neil Lennon insisting the offer was well below their £25m asking price.
The Gunners have reportedly lodged an improved offer, but it is still thought to be short of the Bhoys’ demand.
Meanwhile, Arsenal also fell short in their approach for Zaha.
The Gunners are understood to have offered £40m for the Ivory Coast international.
But like Celtic, Palace rejected the move, insisting they would need to table a significantly improved bid to begin talks.