The left wing-back was due to make his Bucks bow at home against the league leaders but pulled his quad muscle while kicking a ball goalwards as Gavin Cowan’s men completed their warm-up.
The former Aston Villa youngster, 23, had joined Telford from National North rivals Bradford Park Avenue in the build-up to the York fixture as Cowan made several changes to his under-performing squad.
But he is now unlikely to feature for the Bucks until into November after the bizarre setback.
“We’re assessing Riccardo but it’s going to be four weeks,” said Cowan, whose side picked up a creditable point in the 1-1 draw with the Minstermen.
“It was really unfortunate. We were jogging in as a group and he kicked the ball and pulled his quad, it’s desperate for the lad to have something freakish like that.
“It’s about how we manage him now. He was absolutely distraught but I had to tell him before the game it wasn’t about him any more – he had to support the group.
“We’ll get him get through the rehab and monitor him every day.”
Cowan confirmed that skipper Shane Sutton has missed the last two games with an injury to his ankle that showed up after scans.
The boss insisted that stalwart Sutton would have work on his hands to get back into the side after the trio of Theo Streete, Zak Lilly and Billy Sass-Davies were given starts.
Cowan admitted it was a tough test for 19-year-old Crewe loanee Sass-Davies.
“He’s an excellent player for his age,” the boss added. “He was very solid and had his hands full on Saturday but it will be good learning for him.
“It’s a balance because he’s come from Crewe to learn and we understand that but we can’t be accepting too many mistakes.”
Cowan praised the impact of wideman Brendon Daniels, who came in as a last-gasp replacement for the injured Calder.
“His attitude has been phenomenal,” said Cowan. “He has a fantastic character. He is outspoken and has had bad press but wants his voice heard and I love that.
“He wants to be a part of and is fully on board.”