Joel Campbell's play a pleasant surprise to Arsenal, Arsene Wenger

Joel Campbell's emergence as a key player on the wing for Arsenal has surprised even Arsene Wenger, who is happy he refused to let the Costa Rican forward go out on another loan this season.

Campbell began the campaign struggling to even get on the bench for games as he was well behind the likes of Alexis Sanchez, Theo Walcott and Alex Oxlade-Chamberlain in the pecking order for playing time on the wings.

But a string of injuries gave Campbell his chance to claim a regular spot in the lineup over the last couple of months, and he has responded with a number of impressive displays. The latest came in the FA Cup on Saturday, when he scored the equaliser in a 3-1 win over Sunderland and helped set up the second goal.

Wenger said it's clear that Campbell has grown more comfortable with being a regular player for Arsenal, which is reflected in his performances.

"I have a choice on the flank between many players, and he's one of the players who has come in at a very sensitive period," Wenger said. "What is very interesting in Campbell's case is he looks like he has gained more confidence and more authority in his game.

"In the final third he is a dangerous player, and he has shown that. When you look at the player, look at the number of goals he scores, the number of assists, and on that front you must say he has been very positive. And he works hard for the team."

That work rate is one of the qualities that has helped endear Campbell to fans at the Emirates, with his willingness to track back defensively and chase after the ball reminiscent of Sanchez at times. It's one of the reasons why Wenger admitted to being surprised by Campbell's performances.

"But you know, you want to be surprised by the quality of your players. And I think where he surprises you is the intensity of his team work," Wenger said.

Campbell has had to wait a long time for his chance. He signed for Arsenal in 2011 but spent the next two years out on loan as he failed to get a work permit to play in England. Even after that permit was granted, Campbell was sent out to Olympiakos on a year-long loan in 2013-14 and was loaned out again to Villarreal in the second half of last season.

Wenger said Campbell was keen to go on loan again in the summer, knowing that he would struggle for playing time at Arsenal.

"I refused to let him go, because I saw something in him that gives you belief, because of his attitude," Wenger said. "I explained the situation to him [and said], 'Let's have a go, and let's see where you stand in January.' It's a bit similar to [Francis] Coquelin."

Coquelin was last season's revelation for Arsenal when he was recalled from a loan at Watford in January and became the team's first-choice holding midfielder, helping bring added stability and balance to Wenger's team. While Campbell may struggle to hold on to his starting spot when Sanchez comes back, the Costa Rican said he is just trying to make the most of his opportunity.

"Football is like that. It can change from one day to the following one," Campbell told the Arsenal website. "Today you are in the starting lineup and tomorrow you are on the bench. Football is about moments and you have to take them.

"Obviously when someone works well and conscientiously he will always see the fruits, sooner rather than later. I work hard and trust in my ability."

Wenger trusts in him now, too. Especially after seeing Campbell help Arsenal beat his former team Olympiakos 3-0 in a must-win Champions League game that sent the team through to the knockout stages. While it was Olivier Giroud who scored a hat trick in that game, Campbell created the second goal when he held off three defenders before sending the Frenchman clear on goal with a perfect pass through traffic.

Wenger said that performance proved that Campbell can be counted on in big moments.

"I always thought his attitude was right. But at Olympiakos, where we had a game where we had a knife against the throat, he turned up with something special," Wenger said. "He delivered the pass to Giroud on the second goal which was massive for us. Then you think, 'oh he can play under pressure as well,' which is important for us."

With Campbell's performances on the flank, a return to fitness for Walcott and both Sanchez and Mesut Ozil also capable of playing out wide, Wenger is now looking to shape Oxlade-Chamberlain into a central player.