This article proposes a Motivation Assessment-oriented Input-Process-Outcome Game Model (MotIPO), which extends the Input-Process-Outcome game model with game-centred and player-centred motivation assessments performed right from the beginning of the game-play. A feasibility case-study involving 67 participants playing an educational game and measuring their motivation through a questionnaire was conducted. The results have shown statistical significant difference between the motivation to play and motivation to learn, as well as statistical significant relationship between the player's motivation during the game-play and the player's initial motivation. A statistical significant increase in player's motivation to learn about the subject presented in the game was also found. These facts confirm the usefulness of assessing player's motivation from the beginning of the game-play. Furthermore, the results have shown the usefulness of the proposed model for assessing the impact of the game-play on player's motivation.