Alastair Cook has warned members of the England dressing room will "be looking for other employment" if they are unable to reverse their recent run of form.
Cook, who will break Allan Border's record for the most consecutive Tests when he takes the field in Leeds on Friday, accepts that England are "not playing well" at present and knows they have lost their last three Tests at Headingley.
But he has urged his colleagues to "stick together" and "not carry the negatives from the first Test with us to Headingley."
"We need to play better," Cook said in his Sky Sports column. "Test futures are on the line.
"It's never great when you lose, even more so playing the way we did at Lord's. It's a frustrating time for us at the moment as a side; we're not playing well.
"If you want to play cricket for England, you've got to deliver, otherwise we'll be looking for other employment. That's the nature of the beast and, fundamentally, we're not producing out in the middle.
"But we have to stick together as a group. The last thing you can do is play the blame game, and the trick is now to not carry the negatives from the first Test with us to Headingley.
"Again, that's another thing easier said than done. But clearly we are not going to lose every game of cricket ever, it is going to turn around at some stage, and it's down to us to do that.
While disappointed for Mark Stoneman, who was dropped after the Lord's Test, Cook expressed confidence in his replacement, Keaton Jennings.
"It's tough on Mark Stoneman," Cook said. "It's horrible. Playing for England is these guys' dreams, so it's not nice seeing people dropped. I spoke to him on Monday; he was obviously disappointed, as you'd expect, but he has to now go away, score runs and look at areas in which he can improve his game.
"It gives Keaton a great opportunity, and we just need people to grab these opportunities with both hands and to start pushing this side forward, like Jos Buttler and Dom Bess - on debut - did at Lord's.
"He is a very level-headed guy and seems very suited to Test level, in terms of his mental approach. He got a hundred on debut, which shows he can play, but then against a good South African side last summer things just didn't quite go his way."