Aberdeen were left to wonder what might have been as Kilmarnock gained a 1-1 draw in a tight contest at Rugby Park.
Paul Heffernan cancelled out Rory Fallon's opener in the first half but the visitors left Ayrshire with a sense of injustice.
With 10 minutes to go Killie keeper Cammy Bell appeared to bring down Niall McGinn in the box, but referee Euan Norris booked the forward for diving.
Having made five changes to his starting eleven, Brown's men were fast out of the traps. Bell saved well from Rob Milson before Fallon lofted the ball over the goalkeeper from just inside the box to give Aberdeen a deserved lead.
Niall McGinn was exploiting space down the right wing with Ryan O'Leary and Jeroen Tesselaar struggling to deal with the Northern Irishman. He hit the post as the Dons went for a second goal.
Killie equalised five minutes before the break as Mo Sissoko's pass played William Gros in on goal. As he ran towards Langfield, his heavy touch found its way to Heffernan who placed the ball into the net.
Kris Boyd was the talk of Rugby Park pre-match and he made an appearance at the interval to cheers from the home fans.
There was further good news on the striker front for Killie as Cillian Sheridan made his return from a hamstring injury ahead of schedule.
McGinn's penalty claim apart the second half was a more subdued affair.
Both sides tried to find a winning goal with Heffernan testing Langfield while Dons substitute Jonny Hayes was denied by Bell late on.
What the manager said
Kenny Shiels: "The signing (of Kris Boyd) had an effect on today as (Paul) Heffernan and (Jamie) Langfield were outstanding.
"He's made a major contribution to this club and is a legend here - it's great to have a player like that here.
"Aberdeen have quality right through their team, I think after they enjoyed the better of the first 20 minutes and hit the post, that could have killed it off. But we dug in, made some chances and then got the goal we deserved.
"The first 20 minutes of the second half we were bossing it and then Aberdeen started hitting us on the break."
Craig Brown: I've seen it again and it's without a doubt a penalty and a red card.
"I've been told by (SFA Compliance Officer) Vincent Lunny and (SFA Head of Referee Development) John Fleming that if you feel the referee has made a mistake then you are able to say that.
"I had asked the fourth official to speak to the referee and ask him why he didn't give a penalty and a red card to the goalkeeper, but it doesn't make much difference now as it has passed.
"The league is so tight, the decision is disappointing, but the implications are huge.
"We can't totally lay blame on the official as we missed what I would describe as five very good scoring chances."
What the fans said
Rory Fallon fairly loves a volley. About the only thing he's good at.— Michael Sutherland (@MSutherland10) February 23, 2013
Thank the lord for Paul Heffernan— Dave Urie (@KilmarnockDave) February 23, 2013
Craig Brown's probably to polite to criticise the ref for not giving @aberdeenfc a penalty but I'm not. A shocking by Euan Norris.— William Masson (@ohmygiddyaunt76) February 23, 2013
That decision to book Niall McGinn for diving is among the worst I've seen in football.— Andy Skinner (@andydskinner) February 23, 2013