COLOMBO: Mohammad Hafeez roared back to form with a career-best 172 not out as Pakistan made Sri Lanka pay for a failed gamble in the second Test in Colombo on Saturday.

Pakistan, trailing 1-0 in the three-match series, took advantage of Sri Lankan captain Mahela Jayawardene's surprise decision to field first on a good batting track at the Sinhalese Sports Club.

Hafeez led the Pakistani charge with his fifth Test century -- and the first after 10 innings -- as the tourists moved to a commanding 334 for one by stumps on the opening day.

The Pakistan vice-captain has put on 256 runs for the unbroken second wicket with Azhar Ali (92 not out) after sharing an opening stand of 78 with Taufeeq Umar (65).

It was the first time since making 379-4 against India in Faisalabad in 2006 that Pakistan scored over 300 runs on the first day of a Test match.

The century helped Hafeez overcome the disappointment of losing the first Test in Galle by 209 runs, where he led Pakistan in the absence of the banned Misbah-ul Haq.

The all-rounder had been under pressure to retain his place in the Test side after a barren run of 10 innings since making his previous best of 143 against Bangladesh in Chittagong last year.

But Hafeez answered his critics in style, smashing 18 boundaries and a six off Suraj Randiv that sailed over the mid-wicket fence.

“Finally I did something good for my team,” a relieved Hafeez said.

“I have been working hard at the nets. It was tough not to be scoring because the top order has to perform in these conditions.

“I was under pressure, but Taufeeq lifted some of it by his superb batting and then Azhar came and gave me solid support. I just needed some luck and it all came good today.”

Azhar was content to play second fiddle at the other end, scoring just six fours, as the second-wicket pair laid the foundation for a big first innings total.

Azhar will resume on Monday needing just eight runs to complete his third Test century.

Sri Lanka's South African coach Graham Ford admitted the decision to field first backfired, but insisted a lot of thought had gone into taking that call.

“Clearly, we got that wrong, but no one thought the pitch will play so well in the first hour,” said Ford.

“If we had got some early wickets, we would have put Pakistan under pressure.

“The decision to field was not taken lightly. There was a lot of discussion and debate and we all felt it was worth having a crack at the ball. But it did not work out the way we wanted.

“We must give credit to the Pakistan batsmen for playing so well. We now have a lot of work to do.”

Hafeez earned a lucky break just before tea when he was caught down the leg-side by wicket-keeper Prasanna Jayawardene, but television replays confirmed Angelo Mathews had sent down a no-ball.

When Hafeez was on 171, umpire Simon Taufel turned down Rangana Herath's confident appeal for a catch at the wicket even as television replays indicated the ball may have gone off the bat.

Hafeez took time to settle down, making only 20 till lunch, before opening out after the break with attractive strokeplay on both sides of the wicket.

He had scored only 12 when Taufeeq raced to his 14th Test half-century in the 18th over with two successive boundaries off Mathews.

Taufeeq fell just when he had mastered the Sri Lankan attack, edging an intended cut off Mathews to the wicket-keeper.

Misbah returned to lead Pakistan after missing the Galle Test due to a one-match ban for slow over-rates, but frontline seamer Umar Gul was ruled out with an ankle injury.