Manchester United striker Dimitar Berbatov went down under Daniel Agger's challenge, and Ryan Giggs scored the resulting spot kick.
Twenty years after last taking charge of Liverpool, Dalglish's problems mounted 32 minutes into the third-round match when Gerrard was dismissed for a lunge on Michael Carrick.
Also today, Sven-Goran Eriksson's Leicester held his former club Manchester City to a 2-2 draw, Chelsea began its cup defence with a 7-0 rout of manager-less Ipswich and Tottenham advanced with a 3-0 victory over third-tier club Charlton.
Dalglish, who quit as Liverpool manager in 1991, was hired again on Saturday until the end of the season after Roy Hodgson lost his job only six months after being appointed.
Dalglish felt that Berbatov went down too lightly before World Cup final referee Howard Webb awarded the penalty.
And before Gerrard was sent off, United defender Rafael da Silva avoided any sanction for a challenge on Raul Meireles that won the ball but was also two-footed.
"The two decisions are important factors in the game, but if you went into detail about them it would take away from the commitment of the players," Dalglish said. "It's difficult to come here. They are top of the league and when you are down to 10 men and lose a goal in the first minute you need to show commitment, and the players did that and they had great support here today as well."
Berbatov insisted that "of course it was a penalty."
"There was enough contact for me to lose my balance and people know I do not go to ground easily," the Bulgaria striker said. "I thought Liverpool put in a good performance and I thought their 'keeper, Jose Reina, was their best player and made some good saves - but we were the better side."
Manchester City goalkeeper Joe Hart's glaring error enabled Andy King to earn Leicester a replay.
Hart failed to hold onto a cross from Paul Gallagher and King converted the rebound in the 64th.
Sol Bamba gave the second-tier side the lead in the first minute but James Milner and Carlos Tevez scored to put City in the lead before half time.
Eriksson was fired by City in 2008 just before a takeover by Abu Dhabi's Sheikh Mansour turned it into one of the richest clubs in the world.
"We came up against one of the best teams in the country so we must be happy," the Swede said. "We tried to win the game but you have to be careful because if you open yourself up you can get caught, but they did very well today.
"I am looking forward (to the replay) and it is a great experience for all the players. It will be difficult (to get a result) but why not?"
Current City manager Roberto Mancini warned his players they must improve greatly if they are to have any chance of winning the competition.
"We had a lot of chances in the second half but this is the cup, it's important we understand the competition, and to win it we must be better than tonight," Mancini said.
Chelsea went some way to lifting the gloom at Stamford Bridge by crushing Ipswich. Carlo Ancelotti's side went into the game on their worst league run for almost 15 years following a loss at Wolverhampton Wanderers.
Ancelotti's decision to continue last season's policy of fielding some youngsters in the early rounds of the cup worked. Daniel Sturridge and Frank Lampard scored twice, Salomon Kalou and Nicolas Anelka also found the net and Ipswich's Carlos Edwards flicked the ball into his own goal.
After a scoreless first half at White Hart Lane, 19-year-old winger Andros Townsend marked his Tottenham debut with a goal four minutes after the break.
Defoe, who started his career with Charlton, made it 2-0 with a low drive before rounding off the victory by scoring his fifth goal of the season.
