Mattis, a 26 year old former Northern Ireland Under-21 international, will go straight into tomorrow's squad for the trip to Hartlepool. He is said to be a box-to-box midfielder, however his chances have been somewhat limited at Oakwell this season. Mattis' only appearance for The Tykes this season was in the second round of the Carling Cup, in a 2-0 away defeat at Newcastle United.
Mattis began his career with Huddersfield Town, for whom he made 79 appearances. He then moved to Bury in 2004, and went on to make over 100 appearances at Gigg Lane before being sold to Barnsley in January 2007 for £50,000.
After yesterday's news that 2 or 3 loan signings may be in the pipeline today, it is not yet clear whether Mattis will joined by other new faces before the day is over. Walsall-MAD will bring you more news updates as we get them.