Since their bye week the Colts are 2-2, falling to heavy defeats to the St Louis Rams and Arizona Cardinals and struggling to overcome divisional rivals the Houston Texans and the Tennessee Titans.
Irsay wrote on Twitter: "7-4, 2 game lead, 5 to go with our injuries n schedule is something we'd take 3 months ago. But the play n last 10 out of 12 quarters - alarming.
"Must find a way 2 win Division, no excuses, no explanations. Hide weaknesses, accent strengthens. We gotta get our heads out of r butts - wake up!
"We'll close ranks n stick together n believe! We'll get it fixed n earn our Div/Camp Hats/Failure is not an option!! How Bad Do WE Want It."
The Colts face the Titans on Sunday and are 7-4 in their season after week 12.