The 27-year-old has 183 runs in three matches and he attributed his form to the good domestic season he had coming into the tournament.
"This whole year has been good for me. I had a good domestic season and it is important that you carry forward that momentum into Twenty20 cricket. I am very confident that given a chance at any level, I will be able to do the best I can, so I am just motivated enough to get runs on the board," he said.
"When I bat at number three, it's a slot that I really like batting at. It gives me the opportunity to play in the power play (overs). It is important that when a team like Mumbai Indians gives you the opportunity up at the top, you have got to put their faith back in them and show some efforts and get some runs," he told reporters in a post-match conference here.
Mumbai lost their openers - batting stalwarts Ricky Ponting and Sachin Tendulkar - with just a run on the board, but Karthik (86) shared a 132-run stand with Rohit Sharma (74 not out) to propel the side to a massive 209 for 5. "
Obviously Ponting and Sachin paaji are two big wickets. I was thinking that if there would be a good partnership between me and Rohit then it will always help the team," he said. "If you see the team's context, every knock is important considering we were no less than one for two and it was important that Rohit and I put up a big partnership and the way he batted was just beautiful. He was giving me the strike when I required it and towards the end, he hit the big shots after I got out," he added.
Karthik said the wicket wasn't conducive for strokeplay but eased out later. "I think when they (Delhi) were batting, it was even better because there was more dew and the ball was coming onto the bat little more. When we started it was a little sticky so it wasn't easy to play shots at the start. You can see from six overs we could only get run-a-ball," he said.
Asked if this was his best performance in Twenty20, Karthik said, "For me, it is tough to rate knocks as such. I don't remember my other knocks. But I can say this for sure that I felt very good when I was batting."
Karthik currently holds the orange cap and asked if he is thinking about winning it at the end of the tournament, he said, "When you have the orange cap, it's a good feeling. It just goes to show that I am contributing to the team. "If we win this tournament, it is a great thing for us. Orange cap is a good thing but winning the tournament is way more important than any individual effort."
Asked how the 44-run victory against Delhi would help the team, he said, "This tournament is such that momentum and confidence is important but at the same time any team can surprise you on a given day. If we play cricket the way we did today, it will be good for us." The Chennai-born stumper is excited to be playing under Ponting. "It is a pleasure playing with him. The intensity he brings on the field and his captaincy has been out of the world. I am very happy just sharing a dressing room with him. Trying and learning as much as I can. He is a great person to be with and I am enjoying every second with him."
"Probably in terms of runs he has not had a great IPL thus far but just the intensity he brings towards captaincy and trying to bring the unit together (is admirable). He is a great captain and his leadership skills are just beautiful," he added.