Cassidy scored his 11th goal of the season, and first in five games, during Rovers' last npower League One outing - a 1-1 draw at Stevenage at the end of last month.
The 19-year-old, who also spent time at Prenton Park last term, has been forced spearhead to Tranmere's attack in recent weeks following a host of injuries to key players.
"He's a good player, there's no doubt about that, he's up there on merit," Moore said. "You could see last season he was a good player.
"But when you consider at one stage this season we actually had Andy Robinson on seven goals, we had Jean-Louis Akpa Akpro on seven goals and we had Cass on seven goals.
"Unfortunately for us the other two have picked up injuries and they're big misses for a club this size, so Cass is important to us to get those goals at this level."
- Sports & Recreation