Messi had the chance to put Argentina ahead from the penalty spot, but his tame effort was easily kept out by Hannes Halldorsson as the spoils were shared at the Otkrytiye Arena.
The Albiceleste boss claimed that Messi struggled due to Iceland's defensive tactics but stressed that the Barcelona star "is very committed" to the national side.
"To evaluate and characterise Lionel Messi's work is difficult because it was an uncomfortable match for him," Sampaoli told BBC Sport at full time.
"Iceland played very defensively, blocking all spaces but we did everything we could to win.
"Leo is very committed to Argentina."
Argentina return to action on Thursday night against Croatia.