Despite only four goals in their last four matches, finding the net hasn't really been the problem for Arsenal this season. Instead Arsene Wenger's team continues to be undone by frailty in defence.

The back four has regressed badly after a solid start to the campaign. Young goalkeeper Wojciech Szczesny has also begun to look like a liability. Fixing the Gunners' leaky back line has to be Wenger's priority this summer.

Here are five defensive transfers the Arsenal boss could pursue in the summer transfer window.

Martin Caceres Centre-Back, Juventus

Versatile Uruguayan Martin Caceres would bring plenty of top-level experience to Arsenal's back four. Wenger could plot a summer move for the current Juventus stopper, according to

Caceres has also plied his trade for Barcelona and combines savvy and aggression to be a bane to opposing attackers. Capable of operating in the middle or at full-back, the accomplished 25-year-old would be a smart signing by Wenger.

Fernando Amorebieta, Centre-Back, Athletic Bilbao

Adding more aggression to Arsenal's defence has to be a priority. The likes of Per Mertesacker and Laurent Koscielny are just too timid at the back. Athletic Bilbao man-mountain Fernando Amorebieta certainly answers the need for aggression.

Reports from Sky Sports indicate the player is already having discussions with Arsenal regarding a summer move. The towering 27-year-old could be secured on a free transfer and represents an excellent bargain.

His disciplinary record may not make the best reading. However, Wenger should risk a few disciplinary issues if it means fielding more tenacity at the heart of Arsenal's defence.

Daryl Janmaat, Right-Back, Feyenoord

The Daily Mirror reports that Wenger could be tempted by Dutch full-back Daryl Janmaat as a long-term replacement for veteran Bacary Sagna. Janmaat has been exceptional for Feyenoord this season.

He has used his stellar performances with the Rotterdam outfit to earn international recognition in the Netherlands squad. At 23 and technically adept on the ball, Janmaat is the kind of skilful and energetic full-back Wenger favours.

However, he only joined Feyenoord this summer, so Wenger won't find it easy to prise Janmaat away.

Angelo Ogbonna, Centre-Back, Torino

Youthful Torino star has been on the radar of plenty of the game's major clubs. The Daily Express claims Arsenal are one of the interested parties. Quick, intelligent and decisive, there are plenty of reasons why Ogbonna is so coveted.

Arsenal need a skilled defender who can combine ferocity with sound technique and control. Ogbonna is that player. He would cost around £17 million, but many would argue it's about time Wenger spent big to repair his defence.

If the French boss is inclined to fend off the competition, Ogbonna would certainly be worth the money.

Simon Mignolet, Goalkeeper, Sunderland

Arsenal need more than just competition for Wojciech Szczesny, they need an upgrade. Sunderland's Simon Mignolet is exactly that. The agile and commanding 24-year-old is a stubborn shot-stopper, who has acclimatised well to the rough and tumble of the English Premier League.

Arsenal only managed a single goal in two games against the Black Cats this season. Mignolet was the main reason why. That has prompted Wenger to consider a summer bid for the Belgian 'keeper, according to The Sun.

His athleticism and quick decision-making would be a major boost to Arsenal's solidity at the back.

If Arsenal hope to compete for the major trophies next season, they must balance their scoring prowess with a more stingy defence. Wenger should consider the players on this list as major assets at a shaky position.