The England striker has apologised to fans for their narrow escape from relegation this season.
"It does trickle down, it does affect us, you can't lie about that," he said. "It's in any job really. If your top man, your boss, doesn't feel secure, then obviously, to the players, it sends a wrong message out.
"Sometimes you can see it on the pitch. But we are professional footballers and we did the job to stay up. We just need to push on now and just forget about this season. It's a write-off and, again, I'd just like to apologise to everybody.
"I think the manager has learnt a lot this season, about his squad and about the Premier League. It's his first proper big job and to come to West Ham is a massive ask as well because it's a massive club.
"He's handled the pressure quite well because we came in with a weakened squad at the beginning of the season. We had to sell a few players that we'd have liked to have kept so he's had to deal with the cards that he's been given. Sometimes, that's not easy for an inexperienced manager. Hopefully, next season should be better."