Shock reports emerged earlier this month that Ronaldo, 32, is ready to call time on his Real career.
He apparently wants to leave the Spanish capital after being accused of tax evasion.
The four-time Ballon d'Or winner has since been linked with a sensational return to Manchester United, who he left to join Real for £80m in 2009, along with cash-rich French giants Paris St-Germain.
And if Ronaldo does end up leaving the Bernabeu this summer, Aleixo reckons Real could well launch a move to sign Sanchez.
The Chile superstar, 28, will be out of contract with the Gunners next summer and his long-term future with the club is currently clouded in doubt.
"He's had a very good season and he had a very important number with Chile in the national team," Aleixo told Sky Sports.
"He's the biggest scorer in the history, bettered Marcelo Salas, that was a very important player for the Chile national team.
"I think many movements in this market depends on what Cristiano Ronaldo does.
"If Cristiano leaves Real Madrid, this can change all the market."
