The 30-year-old Mexico international, who joined Rangers from Pumas in summer 2017, is out of contract in June.

Herrera cost Rangers £1.5m but only managed two goals in 24 appearances for the Glasgow side.

He was due to spend duration of this season with Santos but has failed to score in 10 outings.

Herrera, who last found the net in a 3-1 win over Partick Thistle in September 2017, switches from the side sitting fourth to one fighting relegation in third-bottom spot.

He had been signed by Rangers when compatriot Pedro Caixinha was manager but fell out of favour under predecessor Graeme Murty and has not played for the Ibrox outfit since February.