The 35-year old has just completed a year long spell in Qatar with Al Rayyan and Wanderers manager Sam Allardyce is said to have offered the former Spanish international a chance to return to Europe should he impress in Bormio.
Hierro is a good friend of current Bolton star Ivan Campo following their days together in Madrid and the trial for the veteran is said to have been as a result of Campo's presence in the Trotters squad.
Midfielder Jordi Cruyff is also being put through his paces by the club following his release from Espanyol at the end of last season and both could earn short term contracts with the club as Allardyce looks to add numbers to his paper thin squad.
Yesterdays Independant newspaper claimed that Bolton have been alerted to the fact that old boy Eidur Gudjohnsen could leave Chelsea following the potential arrival of Kezman from PSV Eindhoven but I assume any interest if at all would be in the form of a loan deal only thus ruling us out of the equation as the likes of Newcastle United are said to be prepared to pay cash to land the Icelander. Gudjohnsen's Chelsea team mate Geremi is also said to be a loan target for Bolton if they can pay towards his wages whilst the Perugia forward Jay Boythroyd, a former England U21 international is once again credited as a Bolton target.
N.B I must stress that summertime is a prime time for speculation and it is often hard to seperate fact from fiction until directed otherwise by the football club concerned