The Hammers find themselves short on options in attack with £15m signing Andy Carroll struggling for pre-season fitness - and McDonald has handed Maiga hope he may be the man to fill the void.
McDonald told the club's website: "Modibo is in the team to score goals and interlink and that side of his game was much better than it has been.
"He was running in behind and causing problems, which is great to see as it stretches teams. It was a huge improvement on the last few games we've played.
"Modibo's ability is there as we paid a fair bit of money for him. When you sign new players sometimes they take a bit longer to settle into the team.
"He has just been waiting for his chance to show what he can do and hopefully he can score goals on a regular basis, try to work out where we want him to run to, hold the ball up and interlink. He's got one hell of a chance to start the season."
Maiga found the net consistently for French club Sochaux before arriving at Upton Park in last summer for an undisclosed fee.