what impression of the mudville nine team does the poem give ?

To some extent, this answer will be based on personal reader opinion and interpretation of the poem. The "Mudville nine" refers to the 9 players that are on the baseball team from that town or city. They are mentioned in the very first line of the poem, and the initial impression isn't a glorious and positive impression. This is because the team is losing by 2 runs with only a single inning left to play. Lines 3 and 4 tell readers that Mudville is up to bat, and the first two batters are both thrown out at first. Things are not looking good, because the Mudville nine can't even secure one base runner. The fans support this notion. Stanza two says that a few "straggling" fans even got up to leave in "despair." The fact that the stragglers are now leaving means that a bunch of others must have left prior to this point. Fans leaving the game early isn't a good sign for your baseball team. Stanza 3 doesn't improve the reader's opinion of the team. We are told that Flynn is a "hoodoo" and Blake was a "cake." A hoodoo is baseball slang for somebody whose very presence is bad luck. "Cake" could have multiple interpretations; however, all interpretations send the message that Blake is also no good. This is why the fans sit in melancholy.

So upon that stricken multitude grim melancholy sat;

Like the fans, the readers are left with an abysmal opinion of the Mudville nine.