Jason Cundy has cautioned Aston Villa over Nicolas Jackson and his ill-discipline after he was booked against Nottingham Forest.The striker was shown a yellow card by referee Andy Madley before half-time in the 2-1 Premier League defeat at Villa Park.Jackson was booked late on in the first half of Villa’s home defeat to ForestGettyTammy Abraham was then brought on to replace Jackson at the start of the second half by manager Unai Emery with the score 0-0.It was a change that didn’t deliver the desired effort on the pitch as Villa extended their winless league run to four.Reacting to the substitution on the GameDay Phone-In, Cundy said: “It’s a big call that, bringing off Nicolas Jackson and bringing on Tammy Abraham at half-time, that’s a big call. “Whenever you see that, you think, ‘Right, he’s obviously not doing what he wants’. If you take a striker off and go with a straight swap… that’s a strange decision, and then it doesn’t work…”Villa fan Ez then called into the show and explained what happened in regards to Jackson’s yellow.“He got needlessly booked in the first half. We were in possession two thirds of the way down the pitch and for some reason, we look back and there’s a Forest player on the floor.”Jackson discipline is a ‘problem’talkSPORT’s resident Chelsea fan Cundy then recalled what he saw in regards to Jackson and bookings at his beloved side before the 25-year-old signed for Villa in a club-record £65million deal.“I promise you now, Nicolas Jackson’s discipline is an absolute disgrace. I watched him pick up red and yellow cards for fun, he won’t learn. He has a discipline problem.”Ez then revealed: “We must have had a little break for an injury or something, and the players gathered around the touchline by Emery. “I could see him absolutely bawling at Nicolas Jackson, and then he didn’t come on in the second half. So, I think it’s a discipline thing.”Jackson was hooked at the start of the second halfGettyEmery is said to have been furious with the striker on the touchlineGettyJackson received 18 yellow cards in 81 appearances at Chelsea and was also shown two straight reds, with Cundy offering more insight into the ill-discipline.“The thing with Jackson, he will pick up a yellow card not for a tackle.“He’ll pick it up for saying something to the referee, pulling someone’s shirt… kicking the ball away, all of that, not when you put in a mistimed tackle.”“His ill-discipline is terrible,” he added. “Maybe that’s it, maybe that’s why Emery has gone, ‘Right, I ain’t having that. I’ve warned you, off.'”Emery revealed after the full-time whistle that the booking played a role in his decision to bring Jackson off.“Nico Jackson had a yellow card and the referee was telling us that he needed to keep calm.Villa lost out on the three points as Thiago bagged a late winner for ForestGetty“If not, he was close to having another yellow card. I know Jackson and he could have one action with his power being dangerous for another yellow. It was my decision.”Jackson’s appearance against Forest was his fourth for Villa since the summer move from Chelsea.Liam Delap and Igor Thiago scored either side of an Alysson goal to hand Forest their first win of the season.