Daly was on the sidelines - he was a substitute as his comeback from hernia surgery continued - when Goodwillie launched himself at Craig Conway's cross just outside the six-yard box. Motherwell goalkeeper Darren Randolph could not keep the ball out after being caught off guard by the audacious effort, which cancelled out John Sutton's first-minute header.
Daly has seen his team-mate perform similar feats on several occasions, most recently when he hit the post in a 3-1 victory over Aberdeen and he said: "It's Goody, isn't it? It's what he does and you expect it from him."
The Irishman added: "He did it last Monday night and was unlucky not to score, he hit the woodwork. He does it quite regularly in training."
Daly himself got on the scoresheet with a more routine, but just as important, finish in the 73rd minute. The former Stockport striker slotted home Danny Swanson's cross 64 seconds after Sutton had put Motherwell back in front in an absorbing quarter-final.
It was Daly's second goal off the bench in four days - his first was an injury-time winner against Hamilton, three weeks to the day since his operation.
"I'm happy enough with that," Daly said. "I'm just happy to be playing, I wasn't supposed to be back for another couple of weeks.
"I don't know if I'm a quick healer, I just did what I was asked to do by the physio and made sure I worked hard, and it's paid off."
Motherwell came closer to claiming a winner but United were determined not to give up their Scottish Cup trophy and are confident of progressing in the replay, which is scheduled for March 29.
"We had success last year and we've got the taste for it and we didn't want to go down without a fight," Daly said. "We're quite happy we're still in the cup. It's going to be a difficult tie going to Fir Park but we're capable of winning it."
Source: PA
Source: PA