Table:
text: 2011–12 Club Nacional de Football season
Squad
Squad
No_ Name_ Position_ Date_of_Birth_Age Signed_from Notes_
– Rodrigo Muñoz GK January 22, 1982 (age 32) Cerro Out on 10 January 2012
– Diego Barboza DF January 9, 1991 (age 23) The Academy Reserve team player
– Sebastián Coates DF October 7, 1990 (age 23) The Academy Out on 26 August 2011
– Gabriel Marques DF March 31, 1983 (age 31) River Plate Out on 29 December 2011
– Gonzalo Godoy DF January 17, 1988 (age 26) Cerro Out on 5 January 2012
– Sebastián Gorga DF April 6, 1994 (age 20) The Academy Reserve team player
– Maximiliano Moreira DF June 11, 1994 (age 20) The Academy Reserve team player

text: 2011–12 Club Nacional de Football season
Squad
Squad
No_ Name_ Position_ Date_of_Birth_Age Signed_from Notes_
18 Israel Damonte MF January 6, 1982 (age 32) Godoy Cruz In on 19 January 2012
19 Andrés Scotti DF December 14, 1975 (age 38) Colo-Colo In on 3 January 2012
20 Álvaro Recoba MF March 17, 1976 (age 38) Danubio Vice-captain
21 Matías Vecino MF August 24, 1991 (age 22) Central Español 
22 Joaquín Boghossian FW June 19, 1987 (age 27) Red Bull Salzburg 
23 Facundo Píriz MF March 27, 1990 (age 24) The Academy 
24 Marcos Aguirre MF March 30, 1984 (age 30) San Martín (San Juan) In on 12 January 2012
25 Jorge Bava GK January 22, 1982 (age 32) Cerro In on 13 January 2012

text: 2011–12 Club Nacional de Football season
Squad
Squad
No_ Name_ Position_ Date_of_Birth_Age Signed_from Notes_
1 Leonardo Burián GK January 21, 1984 (age 30) Bella Vista First team goalkeeper
2 Darwin Torres DF February 16, 1991 (age 23) The Academy Reserve team player
3 Jadson Viera DF August 4, 1981 (age 32) Vasco da Gama AUF player
4 Christian Núñez DF September 24, 1982 (age 31) Cerro 
5 Santiago Romero MF February 15, 1990 (age 24) The Academy Reserve team player
6 Alexis Rolín DF March 2, 1989 (age 25) The Academy 
7 Rafael García MF January 6, 1989 (age 25) Rampla Juniors 
8 Matías Cabrera MF May 16, 1986 (age 28) Cerro 

text: 2011–12 Club Nacional de Football season
Squad
Squad
No_ Name_ Position_ Date_of_Birth_Age Signed_from Notes_
– Nicolás Olivera DF February 17, 1993 (age 21) The Academy Reserve team player
– Fernando Poclaba DF January 23, 1990 (age 24) Racing Out on 31 December 2012
– Agustín Tabárez DF October 15, 1994 (age 19) The Academy Reserve team player
– Anderson Silva MF August 28, 1982 (age 31) Barnsley End of contract on 31 December 2011
– Ayrton Bone MF May 27, 1994 (age 20) The Academy Reserve team player
– Carlos De Pena MF March 11, 1992 (age 22) The Academy Reserve team player
– Hugo Dorrego MF May 9, 1993 (age 21) The Academy Reserve team player

text: 2011–12 Club Nacional de Football season
Squad
Squad
No_ Name_ Position_ Date_of_Birth_Age Signed_from Notes_
9 Alexander Medina FW August 8, 1978 (age 35) River Plate Captain
10 Tabaré Viudez FW September 8, 1989 (age 24) Necaxa 
11 Vicente Sánchez FW December 7, 1979 (age 34) América In on 15 January 2012
12 Martín Tejera GK February 16, 1991 (age 23) The Academy 
13 Pablo Álvarez DF February 7, 1985 (age 29) Panserraikos In on 3 January 2012
14 Diego Placente DF April 24, 1977 (age 37) San Lorenzo 
15 Gonzalo Bueno FW September 1, 1991 (age 22) The Academy 
16 Mathías Abero DF April 9, 1990 (age 24) Racing 
17 Maximiliano Calzada MF April 21, 1990 (age 24) The Academy

Question: What is the total number of ''df'' positions on the list for Club Nacional de Football 2011-12?