Darren Bent is perplexed by Arsenal's decision to allow Joe Willock to join Newcastle United on a permanent deal.

The 21-year-old, who scored in each of his last seven Premier League appearances for the Magpies during a hugely successful loan spell last season, has signed a long-term deal.

Willock completed a £25m move to Newcastle after an impressive loan spell

Head coach Steve Bruce revealed on Friday morning he would be at the club for six years - for an undisclosed fee which it is understood could eventually amount to £25million.

That makes him the club's second most expensive acquisition after £40million striker Joelinton, but he will not be able to make his second debut this weekend against West Ham United.

Conversely, the Gunners have got their new campaign off to the worst possible start after suffering a 2-0 defeat to Premier League new boys Brentford on Friday night.

And Bent believes the club could be making the same mistake as last season when they allowed Emiliano Martinez go to Aston Villa for a relative bargain.

Arteta is under intense pressure already after just one game

"I don't understand why Arsenal let him go so easy," Bent said on Drive. "He is certainly a player that could do a bit of damage.

"We saw he had to kind of bide his time at Newcastle in terms of starting a couple of games and then having to come off the bench a few times.

"But once he got to grips with it in terms of playing week-in, week-out, he was brilliant.

"So again, Arsenal potentially making the wrong decision as they did with Martinez.

"Listen, fair play to Joe Willock; he has to Newcastle, a really good signing from them and well played Steve Bruce."