Write a question about the following article: In early April 1521, the royalist side moved to combine their armies and threaten Torrelobatón.  The Constable of Castile moved his troops  southwest from Burgos to meet with the Admiral's forces near Tordesillas.  Meanwhile, the comuneros reinforced their troops at Torrelobatón, which was far less secure than the comuneros preferred.  Their forces were suffering from desertions, and the presence of royalist artillery would make Torrelobatón's castle vulnerable.  Juan de Padilla considered withdrawing to Toro to seek reinforcements in early April, but wavered.  He delayed his decision until the early hours of April 23, losing considerable time and allowing the royalists to unite their forces in Peñaflor. The combined royalist army pursued the comuneros. Again, the royalists had a strong advantage in cavalry, with their army consisting of 6,000 infantry and 2,400 cavalry against Padilla's 7,000 infantry and 400 cavalry.  Heavy rain slowed Padilla's infantry more than the royalist cavalry and rendered the primitive firearms of the rebels' 1,000 arquebusiers nearly useless.  Padilla hoped to reach the relative safety of Toro and the heights of Vega de Valdetronco, but his infantry was too slow.  He gave battle with the harrying royalist cavalry at the town of Villalar.  The cavalry charges scattered the rebel ranks, and the battle became a slaughter.  There were an estimated 500-1,000 rebel casualties and many desertions. The three most important leaders of the rebellion were captured: Juan de Padilla, Juan Bravo, and Francisco Maldonado.  They were beheaded the next morning in the Plaza of Villalar, with a large portion of the royalist nobility present.  The remains of the rebel army at Villalar fragmented, with some attempting to join Acuña's army near Toledo and others deserting.  The rebellion had been struck a crippling blow.

Question about the article:
How many estimated casualties were there?