Xavi battling to be fit to face Copenhagen
The Spain international has been trying to shake off the injury for several weeks and it forced him off in the second half of Barca's 2-1 La Liga victory over Valencia on Saturday.
"He finished (the Valencia game) with some discomfort and since then he's been improving," Guardiola told a news conference ahead of Wednesday's Champions League Group D clash at the Nou Camp.
"He is unique in many ways but there are alternatives and several players who can do a good job," he added.
Barca central defender Gabriel Milito will definitely miss the Copenhagen game after he damaged a thigh muscle in training on Monday, while forward Pedro is still recovering from a hamstring injury.
Copenhagen top Group D on six points from two matches, with Barca second on four ahead of Rubin Kazan on one and Panathinaikos on zero.
At an earlier news conference, forward Lionel Messi said Barca would miss Xavi if he failed to shake off his injury in time.
"Xavi is extremely important for how he plays and how he dictates play," the Argentina international said.
"In any case, we have enough reserves if he doesn't make it as we have a very strong squad," he added.