Jordan Spieth barely had time to slip his arms into the Masters champion green jacket on Sunday when he took aim at his next target – world number one Rory McIlroy.

The 21-year-old American captured his first major title in historic fashion, matching the 72-hole Augusta National record low of 18-under par 270 to defeat Phil Mickelson and Justin Rose by four strokes.

“It’s incredible. It’s one of the best feelings I’ve ever felt,” Spieth said. “This was arguably the greatest day of my life,” Spieth said.

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Spieth becomes only the fifth man and first since Raymond Floyd in 1976 to post a wire-to-wire Masters victory. In the process he set 36 and 54 hole records for the tournament while his 28 birdies over four rounds smashed Phil Mickelson’s 2001 mark of 25.

The 2013 PGA Tour rookie of the year will jump from fourth in the world rankings to second with the victory, but reigning British Open champion and 2014 PGA Championship winner McIlroy has what the Texan is shooting for next.

“The ultimate goal that I have is try to become the number one player in the world,” Spieth said. “I don’t think I am with this. I think that I’m still behind, and so I’m still chasing that goal. It’s going to be very difficult, but to be a large step closer is huge.

Golf’s new great rivalry?

Rory McIlroy was unable to complete a career Grand Slam at the Masters as Spieth streaked to victory. Photo: Getty

That figures to bring on a rivalry with McIlroy, a four-time major winner who was hoping for his third consecutive major title this week to complete a career grand slam at age 25. Instead, the Northern Irish star settled for fourth, a final-round 66 only good enough to finish sixth behind Spieth.

“As far as with Rory, he’s got four majors. That’s something I can still only dream about,” Spieth said. “I’ll never hit it as far as he does and I have to make up for that somewhere else. He’s an unbelievably nice guy. Carries that world number one with class.

“As far as a rivalry right now, look forward to getting in the heat of the moment with him a couple times in the near future and see if we can battle it out and test our games.”

One of those showdowns could come in July at the British Open at St. Andrews, where Spieth is delighted to be going as the Masters champion.

“To go to the home of golf and what I consider one of the coolest places in the world is going to be really special as the Masters champion,” Spieth said.

“I’m sure that it will be a great time, and I look forward to enjoying the town, the whole experience of playing in an Open Championship at St. Andrews. It’s really cool.”

And in case you thought Spieth might be resting on his laurels, think again.

“Hopefully at that point, maybe try and go for the third leg of a Grand Slam. Can’t win four unless you win the first, right?”

Australian Open remains a priority for Spieth

Jordan Spieth after winning the 2014 Australian Open.

Another date Spieth longs for is his chance to defend the Australian Open crown he won last November, a victory he credits with pushing him along the path that led to his Masters triumph.

“That could arguably be one of the best wins that I’ve ever had. I would obviously call this one the greatest win I’ve ever had – no offense,” he said. “But what the Australian Open did is in a period where I had some struggles … closing out that tournament, it meant a lot.

“It was a special week for me and obviously did a lot for my career. Without it, I may not be here right now.”

Spieth said managing the mental game under pressure was his toughest test and called his eight-foot par putt at the par-3 16th “the key moment.”

“That’s when I really felt like it could get out of my hands if I’m not careful,” he said. “I would call that the biggest putt I’ve ever hit in my life.”

But Spieth also dubbed his tee shot and approach at the par-3 13th to set up a birdie “the two biggest shots I’ve ever hit in my life” as they came after a bogey at 12 that put Mickelson within four.

“I needed to do something. I needed to birdie that hole,” Spieth said.