Former Real Madrid sporting director and coach Jorge Valdano has called on the club to find a solution to Isco's ongoing plight.
The Spain international was a key man for Madrid as they won three consecutive Champions League titles under Zinedine Zidane, but he has fallen out of favour since Santiago Solari took over.
Isco's five La Liga starts this season all came while Julen Lopetegui was at the helm, but Solari insisted there was nothing personal in his decision to leave the 26-year-old on the bench as a weakened Madrid side won 2-1 at Real Betis on Sunday.
Valdano is not impressed, though, and believes there must be issues behind the scenes that need to be fixed.
"A year ago, the great hopes of Real Madrid were Isco and [Marco] Asensio," Valdano told Onda Cero. "One has been lost along the way and the other is under observation.
100% - Real Madrid under Santiago Solari have won 100% of their games without Isco Alarcon in all competitions (6/6), compared to 63.6% with him (7/11). Debate. pic.twitter.com/SdJVtz5Ugs— OptaJose (@OptaJose) January 13, 2019
"Everyone knows that something is wrong with Isco, but nobody knows what is happening. It should be solved in private. Cristo Gonzalez played ahead of Isco [against Betis] - this is a serious problem.
"I suppose it is something that is talked about within the club. Isco must do some soul-searching."
Madrid climbed to fourth in La Liga with the victory on Sunday, but Solari's men remain 10 points behind leaders Barcelona after 19 matches.
Next up for Los Blancos is a Copa Del Rey round of 16 second-leg tie against Leganes on Wednesday, which they head into with a 3-0 aggregate lead.
Solari will then turn his attention to a huge La Liga clash against Sevilla on Saturday, with both sides locked level on 33 points in the table.