Wigan boss Roberto Martinez intends to add more faces to his squad before the new Premier League season begins.[LNB] Martinez has brought in four players so far this summer, with Antolin Alcaraz and James McArthur this week joining Mauro Boselli and on-loan Ali Al Habsi.[LNB]The Spaniard says he is not finished there as he aims to improve on last season's 16th place.[LNB]"There is still a long way to go before the [transfer] window closes," Martinez said. "I expect a few people to come in and hopefully we will balance the squad and be a stronger group of players than we were last season.[LNB]"We want to create a very competitive environment at Wigan Athletic and to do that we need to improve the squad in every window.[LNB]"We will do that and we are always working to do that."[LNB]Wigan yesterday presented Alcaraz and McArthur to the media at a press conference at the DW Stadium.[LNB]Paraguay defender Alcaraz, 27, completed his free transfer from Club Bruges when he was granted a work permit on Thursday.[LNB]Midfielder McArthur, 22, followed when he signed a four-year contract yesterday to complete a move from Hamilton believed to be worth around £500,000.[LNB]Martinez said: "James McArthur is a young, exciting prospect who we have been following for a long time and someone I think is going to go on to full international honours with Scotland.[LNB]"He has a winning mentality, a very strong character and is at a young age.[LNB]"Antolin was one of the best centre-halves at the World Cup.[LNB]"We spotted him really early and managed to persuade him to sign for Wigan Athletic before the World Cup.[LNB]"We signed him on a free and he is a really exciting prospect for us."[LNB]Martinez feels the pair will both fit well into a group which has returned for pre-season training in good spirits.[LNB]He added: "The boys have come back in very good shape and we are delighted with that.[LNB]"I am happy with the players that have come in and happy with the players that have stayed.[LNB]"They have really taken ideas on board and taken responsibility.[LNB]"I am very pleased with that aspect but we will carry on working and carrying on bringing players to remain as competitive as we can."