Nathan Ralph has pulled out of next week’s England C squad and will miss the next six weeks for Kevin Maher's side.
The defender came off at half-time with a quad strain in the 2-0 win against Altrincham last weekend, in which he was on the scoresheet with the opening goal.
But Southend Head Coach Maher confirmed on Thursday morning he will now be out for at least a month.
"Ralphy got injured last Saturday and he’ll be missing for a little period now.
"It’s a grade two so maybe six weeks. Fingers crossed he can recover quickly. He’s a fit lad and he has recovered quickly before, so fingers crossed.
"I’m disappointed for him because he’s been brilliant for us and he fully deserved the call-up to England C.
"It’s disappointing that he will be missing games for us too."