The Argentine has come under criticism in recent weeks following Barcelona's elimination from the Champions League and Copa del Rey final defeat against Real Madrid.
However, Toshack has insisted that Messi is not to blame for the Catalan outfit's troubles, which have also seen them fall seven points behind La Liga leaders Atletico Madrid, albeit with a game in hand.
"It's cruel to blame Messi. You can't put the blame on him. Messi's at a high level but more is always expected from him," Toshack told La Xarxa.
Toshack has managerial experience in Spain having previously been in charge at both Real Sociedad and Real Madrid.