Stimac's youngest daughter Dea suffers badly from asthma, and endured problems while living in London. However, since arriving back in Croatia for a holiday this summer, her condition has improved, persuading the 33-year-old that he should move his family back home and continue his career with Hajduk Split, the club that gave him his break in football.
Igor, who joined the Hammers from Derby County for £600,000 in September 1999, expressed his sadness at having to leave the Hammers via his own personal website (http://www.bigfanof.com), saying: "I am still in Croatia at the moment and I have decided to stay here and join up with my former club, Hajduk Split.
"It was a very difficult decision to make but in the end it was not a footballing decision. Unfortunately my youngest daughter suffers from asthma and since we returned to Croatia she has been feeling much better.
"I spoke with my wife about this and she decided it would be far better to keep the family here in Croatia for the benefit of my daughter. The option was there for me to go back to England and stay with West Ham, but it would have been very hard for me to be without my family.
"My agent has been dealing with West Ham over the last few days and they have been very good and understanding about my situation. Now we are just waiting for the papers to be sorted out so I can register as a Hajduk player again. I have one year left on my West Ham contract but it has been agreed that I can move on a free transfer.
"It's very disappointing for me to be leaving West Ham because I had a couple of great years there. It has been difficult recently with a couple of big players leaving and the manager moving on as well, but I thoroughly enjoyed my time at Upton Park. I actually planned to extend my contract and stay on at West Ham for a little longer but circumstances have prevented me from doing this. I hope the fans understand my position and I wish them and the club all the best for the future."
Manager Glenn Roeder admits: "We have allowed Igor to leave the club on a free transfer for family reasons. I was very sorry to hear about the situation regarding Igor's daughter - I know that she suffered badly with asthma last year.
"Igor is a very family-orientated person and in this situation it would have been wrong of me to demand that he come back to England or prolong the situation by trying to sell him for a fee.
"Although football is important to all of us, a person's family should always come first and that is a policy I have always followed.
"Igor has always been committed to the club and we wish him and his family all the best for the future."
Glenn is now focusing his efforts on strengthening the squad and admits: "With Igor having now left, I most definitely need to bring in one, maybe two, central defenders who will add further quality to the squad.
"I am pursuing that aim very seriously at the moment and my job in the last few days has consisted almost entirely of dealing with possible signings. I have been on the phone virtually every minute and it is absolutely non-stop.
"Only yesterday I was about to start training but then had to dash to France to talk to a player. I got home at midnight last night after a pretty fruitless trip and, although the deal isn't entirely dead, that is the sort of thing you have to accept in this position.
"I am enjoying it though and as well as bringing in one or two defenders, I am also looking at two or three elsewhere for positions further up the field.
"Again, I want to emphasise the fact that the players I want to bring in will definitely improve the team and I hope that the arrival of someone like David James will prove to those players that we are going places and persuade them that Upton Park is the place to be.
"I am looking forward to working with a top quality squad next season and hopefully there will be some exciting developments in the very near future."