A commanding centre-half, Cover secured his first professional contract at Derby in March 2016 following a string of impressive displays.
Cover became a regular feature in the Rams’ then under-21 squad who were promoted as Division 2 champions at the end of the 2015/16 season, ahead of Arsenal.
A captain during his two-year scholarship, Cover was seen as a key figure for the under-18s, which lead to him earning an early promotion to the under-21 squad.
The youngster made his first team bow in a pre-season friendly encounter against Portuguese giants Benfica in the Algarve Football Cup in July 2016 and backed that up by playing fourteen times as the club’s under-23s retained their Premier League 2 Division 1 status at the end of the 2016/17 season.
Alfreton manager McDermott told the club`s official website: "It's exactly what we needed, we are a little light at the moment with Luke Shiels suspended, Billy Priestley out injured so we only have Tom Allan in that position. We are very happy Alex is with us, he will strengthen us and aim to stop letting in goals which has become our habit in recent weeks.
"He is highly rated by Derby and aggressive, he's good on the ball and sharp to react. His fitness will be important for us and his reactions and interceptions will help us sturdy up that back line which we want to be strong. It's a great chance for both to have a look at each other, gives Alex the chance to play and he's a local lad and chose us; so, we are delighted with that and excited to work with him.
"A big thank you to Derby who were brilliant in helping us, we are happy to have Alex here".