The giant Austrian international returns to the San Siro on Wednesday for the second Champions League Group A encounter and is keen to show the European champions what a great player they could have had if he had felt more like a part of the family.
"Now I set three alarm clocks. I am more disciplined these days." Arnautovic told reporters.
"What matters here at Werder is the team. At Inter it was different. There everyone does their own thing."
The 21-year-old was chased by Inter's sporting director Marco Branca for months but when he finally joined on loan from Twente Enschede last year, former coach Jose Mourinho took an immediate dislike to his sometimes lax approach.
He barely featured during Inter's stunning treble success last term and the Serie A champions never considered taking up their option so Twente sold him to Werder.
Arnautovic, comparable to Zlatan Ibrahimovic in his style of play, started the 2-2 draw at home to Tottenham Hotspur on Matchday 1 and is expected to play against Inter given Claudio Pizarro is injured.
MILITO DOUBT
Coach Thomas Schaaf is also without injured left back Sebastian Boenisch, who will be out until early next year, captain Torsten Frings and defender Clemens Fritz but centre-half Per Mertesacker is back.
Werder go into the match on the back of their 3-2 league win over bitter rivals Hamburg SV though they were again erratic, squandering a 2-0 lead before clinching victory with a late winner from in-form Portuguese striker Hugo Almeida.
The sight of Arnautovic will remind Inter and new coach Rafael Benitez of how limited his attacking options are, especially with Diego Milito doubtful with a leg injury.
The holders sold Mario Balotelli to Manchester City in the close season as well as letting Arnautovic go, meaning usual starters Milito, Samuel Eto'o and Goran Pandev are their only established forwards with youngster Coutinho still very green.
"There's no lack of quality alternatives in attack. Players like Milito, Eto'o, Pandev and Coutinho aren't easy to find," Benitez said after Saturday's 1-0 defeat at AS Roma, his first league defeat of the fledgling campaign.
Defender Walter Samuel missed the Roma defeat with a knock so Ivan Cordoba may deputise again as Inter look to bounce back from the 2-2 draw at Twente in their group opener.
Evergreen captain Javier Zanetti could also return having been rested for two games after being heavily winded but Thiago Motta is some way off fitness following knee surgery.
Probable teams:
Inter Milan: 1-Julio Cesar; 13-Maicon, 6-Lucio, 2-Ivan Cordoba, 26-Cristian Chivu; 17-MacDonald Mariga, 19-Esteban Cambiasso, 5-Dejan Stankovic; 10-Wesley Sneijder; 9-Samuel Eto'o, 27-Goran Pandev
Werder Bremen: 1-Tim Wiese; 27-Niklas Andersen, 29-Per Mertesacker, 15-Sebastian Proedl, 16-Mikael Silvestre; 6-Tim Borowski, 10-Marko Marin, 14-Aaron Hunt, 5-Wesley; 23-Hugo Almeida, 7-Marko Arnautovic
Referee: Alberto Undiano Ibanez (Spain)
