Stoke's efforts to sign Bruno Martins Indi on a permanent deal remain at a frustrating deadlock as manager Mark Hughes looks to strengthen his defensive options this summer.Following a successful season-long loan at the bet365 Stadium, Hughes is keen to keep the 25-year-old centre-half and Stoke have agreed a fee with his parent club Porto.However, other issues are holding up the transfer and Martins Indi himself has admitted he is likely to be returning to the Portuguese club at the end of the Premier League campaign. Sunday's trip to Southampton will be the final game of his loan spell and Hughes said: " We are still discussing the deal and speaking to Porto. "Clearly, Bruno is still their player, so we can only dictate and influence that situation up to a point and we have to be patient with it. "It's a little bit frustrating though, I have to say, because Bruno has been fantastic this year. But there isn't just us and Bruno to satisfy. "We are still talking about how we can move it forward but there's a little bit of an impasse at the moment. "We want to improve our defensive positions this summer. We haven't spent a great deal of money in defensive areas since I have been here, so we will look to do that this year." Stoke head to St Mary's having won only one of their last 10 matches and it is a run which has contributed strongly to what will be the club's lowest league finish under Hughes, after ending each of the last three seasons in ninth place. Hughes hopes to end the campaign on a high against Southampton, saying: " In terms of our own well being, it would be better to go into the summer on the back of a victory. "We have one more opportunity to get more points on the board and we will look to do that on Sunday. "It's fair to say that we haven't hit our targets this season, so it is disappointing. It isn't disastrous though, I don't feel. "Everybody wants to be stimulated by progressive seasons, and of the four I have been here this is the first that we have fallen short."