The former Hibernian and Celtic forward has been training with the Sky Bet League One side since last week and on Tuesday played the full 90 minutes of a 2-1 reserve defeat by Wigan Athletic.
The 31-year-old - who has not played a competitive match since being released by Bristol Rovers in December 2012 - has been joined in Cumbria by fellow trialists Paul Reid and Lewis Young. Graham Kavanagh, the Carlisle manager, is will today inform the trio whether they will be offered contracts.
This is the latest trial spell for Riordan, who spent time with Belgian side Royal Antwerp last month and was also training with Alloa Athletic. "Del looked like he needed the game but he does have quality on the ball," said Kavanagh. "I will see what comes about in terms of their personalities and how they are in and around the club."