Gary Rowett praised the impact of Johnny Russell after his strike proved decisive in Derby County's 1-0 win over Burton Albion on Saturday afternoon.
Substitute Russell pounced on a poor touch from Matt Palmer to hammer home on the 82nd minute, breaking the army of Brewers fans' hearts and leaving Albion bottom of the Championship.
Rowett, who ended his playing career at the Pirelli Stadium and started his managerial career there, was glad his side were able to come through a difficult spell in the second half where the Brewers gathered some momentum.
And it was Russell - signed by Burton boss Nigel Clough - who proved decisive once the Rams negotiated a tricky spell in which Ben Turner saw a header cleared off the line by Andreas Weimann.
"I think after we made the substitutions, there was probably about a five-minute spell where it went a little bit flat," Rowett said.
"You just knew they were always going to wait for that chance.
"They had one or two set pieces, one that got cleared off the line by Andi Weimann and there were just some moments where you thought 'please don't let them score, because it's going to be a bit similar to Ipswich (Tuesday night's 1-0 defeat) where they're hanging onto a lead.'
"But as it was, we kept going and I think it was their first mistake.
"I think it was Matt Palmer that perhaps could have cleared it and takes a touch.
"I'm sure Nigel will be disappointed but they worked so hard for him today, and they just seemed to get a toe to everything and a last ditch challenge.
"But Johnny was there, and it was a very, very good reaction from him - a great opportunistic strike.
"And that's what you want your subs to do, you want them to come on and have an impact."