Petrov has been undergoing regular spells of treatment since first being diagnosed with the illness last month. The midfielder opted to visit Villa's Bodymoor Heath training complex last week and is feeling "positive" about the challenges ahead, according to Cowans.
He said: "Stiliyan was up at the training ground last week, looked really well and was feeling positive about himself. He's got a hard week this week (with treatment) but he is a fighter and will come through this. He was so bubbly and he came in. He took his hat off and has shaved his hair and looked very well. He is very positive he is going to beat the illness."
Cowans is urging Villa to win their battle to steer clear of the relegation zone in honour of Petrov.
He said: "It has been uplifting and the rest of the lads need to look at that. Everyone is on his side and behind him. What we really need to try for Stiliyan is get ourselves out of the mess we are in at the moment.
"It is a massive week for the club with a big game coming up at the weekend against Sunderland and next Tuesday's meeting with Bolton."
Cowans was speaking after completing the finale of the latest leg of Sir Ian Botham's walk across Britain - from Birmingham to the Clent Hills in Worcestershire - to raise money and promote awareness of leukaemia.
Botham said: "Stiliyan was diagnosed very quickly, has had his first treatment in London and I've heard it is all going very well which is good.
"He is young, fit and strong. It just shows you that this illness can strike anyone. He is one of the fittest young men in the area and look what happens.
"He will be very positive and that is the way to tackle these things. You tackle them front on. It's actually tougher for the family, the loved ones, because you are the one having to do it and just get on and battle away."
Source: PA
Source: PA