31-year-old Nicholls, who made almost two-hundred and twenty first-team appearances during a seven-year spell with the club, is currently a free agent after leaving Crewe Alexandra at the end of last season.
The Stourbridge-born striker left the Saddlers at the start of the 2012/13 campaign when he signed for Northampton Town, a club where he would fail to make an impact - earning just twenty-nine appearances over three seasons - as he struggled to force his way into the team.
After enjoying two loan spells with Exeter City, Alex joined the Grecians on a permanent basis in January 2015 and would go on to make sixty-one first-team appearances over the next 18-months.
After leaving St James Park Alex joined Barnet in July 2016 and went on to score on his debut, against Cambridge United, later that summer. He would notch a total of forty-seven appearances for the Bees along with a loan spell with Scottish Championship outfit Dundee United - Nicholls picking up a Scottish Challenge Cup winners medal when Dundee beat St Mirren in the final - before heading out on the road once again last summer.
Alex penned a one-year deal with Crewe Alexandra last summer and would make twenty-six appearances before being named among a host of players to be leaving the club this summer as they look to rebuild their squad ahead of the upcoming campaign.
Alex was among the Saddlers' side which slipped to a narrow defeat to Alfreton Town on Saturday afternoon as he and former Wolves duo Jonathan Flatt and Liam McAlinden took to the field for the second half as manager Darrell Clarke took a look at some of the options which are currently at his disposal.
With Morgan Ferrier, Josh Gordon, Elijah Adebayo and Match Candlin already among the Saddlers' strikers, the club are likely to offer just one of their striking trialists a deal, o they will both be keen to impress over the coming weeks as we edge ever-closer to the start of the season.