Eddie Howe is hopeful Kieran Trippier will play for Newcastle United again this season, but stated the right-back's injury is "significant".
Trippier was the first arrival under Howe and the new ownership at Newcastle last month, and has played a key role in helping the Magpies turn their form around.
Newcastle are out of the bottom three in the Premier League after three successive victories, beating Leeds United, Everton and Aston Villa respectively.
England international Trippier has scored in both of the last two matches, but he sustained a fracture in his left foot during the win over Villa.
Newcastle confirmed on Monday that the 31-year-old had fractured his fifth metatarsal bone, though no timescale was placed on his return.
Initial reports suggested that Trippier would need between eight and 10 weeks to fully recover.
On Friday, while previewing Newcastle's clash with West Ham, Howe confirmed Trippier's surgery had been a success.
"He had his operation yesterday and that went well, so that was good news," Howe told a news conference.
"We aim to have him back before the end of the season, but it's a significant injury which is a big blow for us."
Trippier's back-up, Javier Manquillo, suffered an ankle injury in the Villa match, and Howe confirmed the Spaniard would also be missing against West Ham on Saturday.
"Manquillo went off in the same game after landing awkwardly on his ankle following a header," Howe said. "We don't think that's serious, but he will miss the game. Apart from that, we're as we were."
A fellow new arrival in January was midfielder Bruno Guimaraes, though the Brazil international is yet to make his full debut for Newcastle, having instead had to settle for two substitute appearances.
"It's a really strong area, probably our strongest in terms of personnel," Howe said of Newcastle's midfield. "Every player would have an argument to say I deserve to start so long may that continue.
"Bruno will start a lot of games for us and will be a huge player. I don't think this period where he's watching and learning from the Premier League is a bad thing for him, although it will frustrate him because he wants to show his talent."
Due to gale-force winds hitting the United Kingdom from Storm Eunice, Newcastle will not be flying down to London, but instead they faced a seven-hour coach journey to the capital ahead of Saturday's early kick-off.
However, recent history is on their side. Newcastle have won their last two Premier League away games against West Ham, and have tasted victory on the road against the Hammers 10 times. They have not won more often on the road against any other side in the competition.
