This paper deals with a case study of the collaboration between sculptors and painters in the context of the construction of altarpieces in 17th-century Spain. It analyses a drawing by Francisco Rizi (Madrid, 1614-Escorial, 1685) in the British Museum depicting a sculptural group and fragments of an architectural framework, and relates it to two other drawings by the same artist in the National Library of Spain. They are identified as fragments of the design drawing of the former altarpiece of the Expectant Virgin in the church of the Calced Trinitarians in Madrid.