There was good news and bad news for West Ham United yesterday when Craig Bellamy and Robert Green combined to deliver a much-needed victory — but also increased their resale values and made it more likely that they will be sold.

For Portsmouth, the news was also mixed — their slide down the Premier League table gathered pace, but supporters might be relieved that Jermain Defoe, the England forward, played poorly enough to convince possible buyers not to bother making a bid.

In a ridiculously open game during which the defences played as if they had hangovers, West Ham scored as many goals as they had in their previous 11 matches and even the misfiring Carlton Cole got on the scoresheet, but Portsmouth could have matched them but for the form of Green in the visiting team’s goal. At the other end, the form of Bellamy, the Wales forward, may persuade Harry Redknapp, the Tottenham Hotspur manager, to increase an offer of £6 million that was rejected on Christmas Eve after scoring the two goals that sealed an overdue first win in five matches.

“He scored two very important goals for us,” Gianfranco Zola, the West Ham manager, said. “There’s so much speculation about him, but as far as I’m concerned, he’s a West Ham player. He’s an important player for us and the club knows I don’t want to sell him. Between me and Gianluca Nani [the technical director] and Scott Duxbury [the chief executive] there is a total understanding. We work together and we’ll try to keep all our players. For the moment, everybody wants to improve this team but we have to see what happens.”

West Ham remain below Portsmouth, but they could change places tomorrow when Stoke City visit Upton Park and Tony Adams takes his freefalling team to Arsenal. This was their second successive home defeat by a three-goal margin and they have won only twice in the 11 Premier League matches since Redknapp left to take over at Tottenham.

“We’ve had two very bad results at home and a bad performance at Bolton, but there are positives,” Adams said. “We are creating chances and going for games, but we’re getting done quite often on the counter-attack, which is worrying.”

They had an almost perfect start when West Ham watched Glen Little cross unopposed, Peter Crouch brought down the ball unchallenged and set up the unmarked Nadir Belhadj. But an error by David James allowed Jack Collison to level after 22 minutes, his shot through a crowd of players passing between the legs of James, who is beginning to look his old fallible self more and more often these days.

West Ham could have gone ahead a minute before the interval when Bellamy nicked away the ball from James, but Mark Noble’s attempt to chip into the empty net was poorly executed and Sol Campbell was able to head clear. But Portsmouth had an even better chance in first-half injury time when Crouch went down under a challenge by Lucas Neill. Steve Bennett, the referee, awarded a penalty, and Defoe, in front of the gleeful West Ham fans, hit his kick into the hoardings. Defoe also failed from the spot against West Ham when playing for Spurs in November 2007, Green saving on that occasion.

Adams said that if players’ heads had been turned by transfer rumours, “then goodbye — they’re no good to anybody”, but denied that he was referring to a specific player. However, the miss was the low point of a display that made you wonder whether Defoe’s mind is not already elsewhere.

“The way Craig Bellamy played, perhaps you could link a few of my players with other clubs,” Adams joked. “Defoe needs a goal. I want him to stay here and I’ve had no offers. If the penalty goes in, I think we run out winners today.”

Instead, West Ham took the lead after 67 minutes when Collison shot against the inside of the far post and Cole swept in the rebound from eight yards. It was only his fifth goal in 17 matches this season.

It could have been 2-2 two minutes later, but within three, it was 3-1. Marc Wilson’s header from a corner hit a post as Portsmouth looked for an instant equaliser, but West Ham cleared to Bellamy, who outpaced the defenders and charged into the area. James managed to block when the Wales forward rounded him, but Bellamy coolly collected the loose ball and scored. He made it four three minutes from time from Luís Boa Morte’s cutback and nearly claimed a hat-trick that would have been a reward for being a thorn in Portsmouth’s side all afternoon. He is suspended against Stoke tomorrow, and if he has played his last match for West Ham, he ensured that he left on a high.

Portsmouth 4-4-2: D James 5 M Wilson 5 S Distin 5 S Campbell 4 N Belhadj 5 G Little 5 S Davis 6 R Hughes 5 N Kranjcar 6 J Defoe 4 P Crouch 6. Substitutes A Traoré (for Little, 71min), Kanu (for Defoe, 73). Not used J Ashdown, H Hreidarsson, P Bouba Diop, D Nugent, N Pamarot.

West Ham 4-4-2: R Green 7 L Neill 4 C Davenport 6 M Upson 5 H Ilunga 5 V Behrami 6 S Parker 7 M Noble 6 J Collison 6 C Bellamy 7 C Cole 6 Substitutes J Faubert 6 (for Neill, 46min), L Boa Morte (for Noble, 72), D Tristán (for Cole, 85). Not used J Lastuvka, H Mullins, J Collins, D Di Michele.

Att: 20,102
Referee: S Bennett.

Star man: Robert Green
Scott Parker and Craig Bellamy had strong claims, but the West Ham goalkeeper made some excellent saves. The West Ham fans pointedly chanted “England’s No 1”.

Window watch

Both clubs are likelier to sell than buy, so more gaps may need filling next month. Portsmouth have lost three top-quality holding midfield players since winning the FA Cup and also need a genuine right-sided attacker. For West Ham, getting Dean Ashton, above, and Kieron Dyer fit would minimise the damage caused by any departures.