Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Exit Date | Pos. | Player | To club | Transfer fee |
| --- | --- | --- | --- | --- |
| 2 July 2008 | GK | Andreas Isaksson | PSV Eindhoven | Undisc. |
| 2 July 2008 | DF | Sun Jihai | Sheffield United | Free |
| 4 July 2008 | MF | Geovanni | Hull City | Free |
| 14 July 2008 | FW | Georgios Samaras | Celtic | Undisc. |
| 30 July 2008 | FW | Bernardo Corradi | Reggina | Free |
| 07 Aug. 2008 | FW | Paul Dickov | Leicester City | Free |
| 23 Aug. 2008 | FW | Rolando Bianchi | Torino | Undisc. |
| 01 Sep. 2008 | DF | Vedran Ćorluka | Tottenham Hotspur | £8.5m |
| 02 Sep. 2008 | FW | Emile Mpenza | Plymouth Argyle | Released |
Question:
What club received a DF player for free?
Answer:
Sheffield United