Rafael Nadal has resisted a serious challenge from Bulgarian dangerman Grigor Dimitrov to soldier his way into the Australian Open semi-finals at Melbourne Park.

The Spanish braveheart had to overcome a savage blister, a one-set deficit and an unusually shaky serve to advance with a typically tenacious 3-6 7-6 (7-3) 7-6 (9-7) 6-2 triumph on Wednesday.

Nadal’s reward is a Friday night blockbuster with four-time winner Roger Federer or Wimbledon champion Andy Murray.

The top seed will require urgent attention to a deep wound on his racquet hand after twice needing extensive re-taping for the injury during his intense three-hour, 37-minute struggle with Dimitrov.

Tipped as a future world No.1 and dubbed “Baby Fed” for a silky playing style uncannily similar to Federer, Dimitrov showcased all his talents – including an audacious under-the-legs lob – to push Nadal to the limit.

Relief … Rafael Nadal reacts after beating Grigor Dimitrov.

The 22-year-old had multiple set-point chances to seize the pivotal third set, only for Nadal to rally to a spirited four-set victory.

The signs were there early that Nadal might be in for a long afternoon when a couple of uncharacteristic shanks handed Dimitrov a break in the second game of the match.

It was the only opening the underdog needed as he clinched the first set with a thundering ace.

Upping the ante, Nadal whipped a signature off-forehand winner to break Dimitrov for the first time to creep ahead 2-0 lead in the second set.

But the top seed gifted the break right back with possibly the sloppiest serving game of his celebrated career.

Three double-faults, a forehand wide and an unsuccessful challenge from the 13-time major winner allowed Dimitrov back on level terms.

That way it remained until Nadal ripped a forehand down the line to create three set points in the second-set tiebreaker.

He only needed one, the Spaniard celebrating like he’d won the title after sending a ridiculous backhand flick past the 22nd seed to square the match up.

Nadal saved a break point early in the third set before gaining another break of his own in the fourth game when Dimitrov sliced a backhand into the net.

A trainer treats Rafael Nadal’s blister during the Spaniard’s match against Grigor Dimitrov.

Clearly bothered by the nasty big blister, Nadal called for the trainer for the first time midway through the third set and moments later coughed up his sixth double-fault to hand back the break.

Another framed forehand had Nadal down set point at 5-6, but he conjured up three big serves to hold and force a second tiebreaker.

The Spaniard found himself staring down another set point after two wayward forehands, but Dimitrov will rue dragging a forehand of his own wide with Nadal on the hop and the court open on his second set point.

And he will certainly curse pulling another identical forehand wide to enable Nadal to nab the third set and claim the lead for the first time in the match.

Two scorching backhand passes earned the top seed the decisive break early in the fourth set and, when he grabbed another in the eighth game, the contest was all over.

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