Brighton boss Oscar Garcia branded his side's 2-1 defeat by Derby in the first leg of their Championship play-off semi-final "unfair".
The Seagulls led through Jesse Lingard's early strike but County's top scorer Chris Martin levelled from the penalty spot for his 24th goal of the season.
The striker then saw his long-range effort come back off the crossbar and bounce in off the back of luckless Seagulls goalkeeper Tomasz Kuszczak in first-half stoppage time.
Garcia had no complaints about Derby's penalty, awarded after a clumsy foul by former England defender Matt Upson on Craig Forsyth.
But he was unhappy with referee Roger East's decision not to award his side at least one spot-kick after Inigo Calderon and Leonardo Ulloa were both sent tumbling in the area.
"It was totally unfair result," said the Spaniard. "We were better than them in all areas apart from the most important area, in front of goal.
"If the referee had given us the penalty it would have been an even better start for us, and then another in the second half. But the referee didn't give them and that's it."
Brighton pushed hard for an equaliser in the second half but Rams keeper Lee Grant stepped up to the plate with stunning saves from Leonardo Ulloa and Stephen Ward to ensure County take a slender lead back to the iPro for the return on Sunday.
It means Steve McClaren is now 90 minutes from a return to Wembley for the first time since his tenure as England manager came to a sad and soggy end under an umbrella in 2007.
The Rams boss said: "That game had everything. You saw every side of Derby.
"We started badly, they started well, but we showed great character to come back and could have had a couple more. But the job is only half done."