Real Madrid buoyed by Alvaro Morata's performance
As a result of Ramos red card, Morata was withdrawn after just 27 minutes as Mourinho looked to offer more defensive cover with the introduction of Raul Albiol but Karanka believes he did all that he could to show he is deserving of more opportunities in the first team.
Real Madrid assistant manager Aitor Karanka was delighted with the contribution of 20-year-old striker Alvaro Morata after their 2-0 win over Rayo Vallecano on Sunday.
But he called into question the judgement of referee Jose Luis Paradas Romero after he sent-off Sergio Ramos after just 18 minutes.
Morata and Ramos had already given the hosts a commanding 2-0 advantage inside the opening 12 minutes, but the home fans were left furious after Ramos was shown a second yellow card for handball and Rayo's Lass Bangoura escaped the same punishment for a similar offence in the second period.
Paradas Romero was also at the centre of a controversial encounter between Villarreal and Madrid last season when he sent-off Ramos, Mesut Ozil and sent Jose Mourinho from the technical area and Karanka was far from impressed with the official's display.
"It doesn't surprise anyone, we already have experience with this referee," he said.
"It was a very entertaining match to start with as Rayo were showing what they are capable of and we had started well in scoring the two goals before the red card came and spoiled the spectacle for the fans.
"The situation with what constitutes a yellow card for handball is confusing for everyone. It would be better for the players, fans and coaches to know how the rule is interpreted than have this confusion."
As a result of red card Morata was withdrawn after just 27 minutes as Mourinho looked to offer more defensive cover with the introduction of Raul Albiol but Karanka believes he did all that he could to show he is deserving of more opportunities in the first team.
"Everyone is desperate to see players from the academy and he has developed a lot this year in the few chances he has had in the first team.
"He scored an important goal at Levante and today he scored as soon as the game kicked off so he just has to take the opportunities he is given and we will always pick the best players as we see them for each game."
Rayo boss Paco Jemez meanwhile was disappointed that his side didn't make better use of their man advantage.
"It wasn't for a lack of trying because we fought until the end, but we lacked definition in front of goal and I didn't expect that," he told reporters.
"We had some chances to score but we should have done more to do more damage in the final third of the field because we have the players to do so. We lacked a bit if bravery in the final third because most of our attacks fizzled out to nothing."
The win allowed Real Madrid to cut the gap on Atletico Madrid in second place to four points with Barcelona a further 12 clear at the top.
Atletico Madrid moved back to within 12 points of the leaders with a comfortable 3-0 win over Valladolid.
Radamel Falcao got the visitors off to the perfect start with his 20th league goal of the season as he pounced from a yard after Dani Hernandez had made a fine save to deny Diego Godin.
Diego Costa then made it 2-0 seven minutes into the second-half as he smashed home Koke's knockdown and Cristian Rodriguez rounded off a first away win in six league games for Diego Simeone's men in stoppage time.
Real Sociedad missed the chance to close the gap on Malaga in fourth place to three points as they could only draw 1-1 at home to Levante despite their opponents having a man sent-off for incredibly the eighth successive league game.
Both goals came in the first-half as Carlos Vela's penalty gave Sociedad the lead before Jose Barkero levelled, also from the spot, nine minutes later.
Valencia did though close to within three points of Malaga despite losing Tino Costa to an early red card as second-half goals from Ricardo Costa and Roberto Soldado gave them a 2-0 win over Mallorca and Espanyol also continued their fine run with a 1-0 win over Real Betis thanks to Sergio Garcia's solitary goal.