The midfielder was brought on with the Hatters trailing 2-0 against Blackburn Rovers at Ewood Park in the Championship.
Despite coming on in the 62nd minute, Walsh lasted just 13 minutes before being given a straight-red for serious foul play.
It's the second time this season that the midfielder has committed such an offence, lasting just 36 seconds in the four-goal thriller with Oxford United back in October before being sent.
Given that this has happened twice now, Walsh certainly felt the wrath of one teammate.
After being shown the red card by the referee, the 27-year-old was arguing his case when Luton forward Carlton Morris approached him.
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Giving him a push towards the tunnel, Morris could be seen making his feelings known before pushing him again and shoving him off the pitch.
It now means that Walsh will serve a four-match which means that he'll miss the entire festive schedule and return to action on January 6.
Discussing the red card with talkSPORT, Luton boss Rob Edwards said: "He's not a bad kid and he's not done it on purpose to injure someone or go in in a dirty way but it's a very similar tackle and it's happened twice when he's come on.
"We've got to look at it.
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"He's obviously cut up in there because of what's happened but we brought him on because he's a technical player and with us being behind I really thought he could help us create something and we did.
"We kept pushing and he was involved in the game but he's made a mistake."
Luton's defeat means that they sit 19th in the Championship with just six wins from 21 games.
The Hatters are next in action on December 20 when they host Derby County.