Avram Grant made many changes from the side that drew at Sunderland. Begovic replaced the ill David James, Finnan came in for the suspended Kaboul whilst Boateng, Diop, Mokoena, Mullins and Piquionne also started.
The home side completely dominated the first period as they had the lion's share of the possession and pinned Pompey back in their own half constantly. Whenever Pompey did win the ball they just kept giving it back, piling more pressure on themselves yet dealing with whatever Chelsea threw at them quite comfortably.
However, after a few sighters, Chelsea took the lead after our defence failed to mark Nicolas Anelka who was found in the box after Alex got down the wing, leaving the Frenchman in plenty of space to simply tap in an easy goal.
Pompey created hardly anything in the first half yet could have poached an equaliser when Piquionne's shot was only parried by Cech. Hermann Hreidarsson got to the rebound but couldn't control it and so the danger was averted.
Tal Ben-Haim wasted the best chance of the half after putting his header over from a free kick, and given how Chelsea had been wavering in their defending of set-pieces recently, you felt that it was a golden opportunity to score.
But come five minutes into the second half and Pompey shocked Stamford Bridge by equalising from virtually nothing. O'Hara's free kick deflected off a couple of Chelsea players and the ball fell to the feet of Freddie Piquionne who blasted the ball past Cech to send the travelling fans into raptures.
Suddenly the belief came flowing back and twice Kevin-Prince Boateng could have given the visitors a dream lead. Ashley Cole denied him a close range shot at goal with a last ditch challenge and then the German (or should I say, Ghanian) found himself in acres of space in the box only to slip at the vital moment.
Still, Chelsea continued to waste their chances or have their shots saved by Begovic who impressed again, and the home fans were getting frustrated whilst those in Pompey blue were thinking of taking a precious point from the league leaders.
Unfortunately, Marc Wilson undone all of that hard work with a stupid and rash challenge on Ivanovic in the box which handed the hosts the most nailed-on penalty you'll see all season.
Frank Lampard scored against us from the spot yet again to seal the win for the Londoners and it might have been worse after Borini read Ben-Haim's woeful backpass and rounded Begovic only to slot the ball wide of the goal.
That meant that Carlo Ancelotti broke Pompey hearts yet again and Avram Grant was denied a dream return to Stamford Bridge, but Pompey can take some heart from their second half performance.
What matters now is that the players carry that on to another tough game against Liverpool on Saturday. The Scousers might be struggling in context of their own season but we'll have to be at our best to get anything from that game.
Pompey Player Ratings
Asmir Begovic: 7 - A few fine saves.
Steve Finnan: 6 - Solid enough.
Tal Ben-Haim: 6 - Should have done better with his header, but good defending.
Marc Wilson: 5 - Costly challenge.
Hermann Hreidarsson: 6 - Stood up well.
Aaron Mokoena (Utaka 83): 5 - No better than usual.
Jamie O'Hara: 6 - Inconsistent.
Hayden Mullins: 5 - Didn't see much of the ball.
Papa Bouba Diop (Hughes 60): 6 - Getting back to full fitness.
Kevin-Prince Boateng: 6 - Our best midfielder on the night.
Frederic Piquionne (Dindane 72): 7 - Took his goal brilliantly and supported the midfield well.
Substitutes
Jamie Ashdown
Nadir Belhadj
Anthony Vanden Borre
Richard Hughes (Diop 60): 6 - Got stuck in.
Hassan Yebda
John Utaka (Mokoena 83): N/A - Last, desperate throw of the dice.
Aruna Dindane (Piquionne 72): N/A - Failed to make anything happen.