Middlesbrough continue to hold on to top-flight survival by their fingertips after a dramatic injury-time equaliser by on-loan striker Marlon King.

Portsmouth had appeared to be strolling to victory thanks to Peter Crouch's crisp 30th-minute volley, with the home side anticipating being booed off by a frustrated crowd.

Instead, 10-man Boro secured what could turn out to be a lifeline with King's fierce strike after David James' top-class save fell to him.

Gareth Southgate's side had been staring the drop in the face, now they were celebrating an unexpected draw. On such moments can seasons turn.

Portsmouth had been good value, dominating throughout and manager Paul Hart will have been furious they allowed victory to escape.

That was even more the case given Boro had only just lost Matthew Bates to a red card for two bookings, the second for a wretched dive in search of an equaliser.

It had all started so well for the visitors, refreshed from a break in Dubai, who had assumed control with two holding midfielders, Sean Davis and Hayden Mullins, restricting the flow in the middle.

David Nugent almost struck early - only Robert Huth's block at point-blank range kept him out after Glen Johnson's powerful surge to the by-line.

Then Crouch attempted one of his notorious overhead kicks after Jermaine Pennant had tempted him with a floated pass - but only succeeded in making contact with David Wheater's face. Fortunately for the Boro defender, he was soon back on his feet.

Nugent was soon cursing his luck even more. First Pennant's deep cross was headed by the England one-cap wonder to Crouch who neatly teed up his strike partner with a return pass for a fierce shot that crashed back off the post with Brad Jones beaten.

Boro tried to relieve the pressure with Stewart Downing having a shot deflected a couple of yards wide, and then Tuncay heading McMahon's corner into the side-netting.

But on the half-hour Portsmouth finally gained the lead. The goal was partially self-inflicted in that Boro fell asleep at a short corner, Johnson picked up the ball and chipped a short pass for Crouch to smack home on the volley from the edge of the box.

Niko Kranjcar almost made Boro pay for more lazy defending, the Croatian bundling through several challenges before seeing his strike deflected over.

Crouch nearly glanced in another before Jeremie Aliadiere and Julio Arca at least gave the home fans some hope for the second half with shots that both deflected for corners.

Middlesbrough desperately needed to up their game after the break but seemed incapable of doing so. As the home crowd's frustration increased, Bates went into the book for a nasty-looking high tackle on Kranjcar.

The Croatian was not hurt though, and soon after landed a dipping free-kick on the roof of the net with Jones apparently beaten.

Southgate had seen enough and sent on Adam Johnson for Aliadiere, and the 21-year-old hit a stunning effort from 25 yards with his first touch but straight at James.

That inspired Boro and James made a quite brilliant save to claw away Tuncay's header from Johnson's cross just when it seemed the Turkish forward had grabbed an equaliser.

At the other end, Crouch latched on to a long ball but it seemed to take an age to drop and Huth was able to head clear.

There was another glimpse of salvation when Downing was put through on the right King but again James got his positioning just right.

Southgate's final throw of the dice was to send on Afonso Alves - the Brazilian striker had missed the previous game due to illness. But Boro's fate looked sealed however when Bates picked up a second yellow for a blatant dive under challenge by Richard Hughes.

Crouch tried to make the match safe but pulled his shot woefully wide, before Downing brought a smart save out of James again.

Bizarrely, the dismissal inspired Boro and they threatened several times in the closing minutes.

The game was two minutes into injury time when King grabbed his equaliser. James looked to have pulled off another tremendous save to keep out McMahon's header only for King to volley home from eight yards.

Amazingly, Alves could have had an unlikely winner when put through one-on-one with James but the England keeper this time had the last word.

Portsmouth's players were left slumped on the ground at the final whistle, wondering how they had let this one slip.

Teams:

Middlesbrough Jones, McMahon, Wheater, Huth, Pogatetz (Taylor 46), Aliadiere (Adam Johnson 58), Arca (Alves 71), Bates, Downing, Sanli, King.

Subs Not Used: Turnbull, Emnes, Shawky, Walker.

Sent Off: Bates (77).

Booked: Bates.

Goals: King 90.

Portsmouth James, Johnson, Campbell, Distin, Hreidarsson, Pennant (Belhadj 36), Davis, Mullins, Kranjcar (Pamarot 90), Crouch, Nugent (Hughes 70).

Subs Not Used: Begovic, Kaboul, Utaka, Kanu.

Booked: Belhadj, Nugent, Johnson.

Goals: Crouch 30.

Att: 24,281

Ref: Martin Atkinson (W Yorkshire).