Motherwell manager Graham Alexander admitted his side were out-fought by local rivals Airdrie as they fell to a 2-0 Premier Sports Cup defeat.
The Diamonds secured the bragging rights after spectacular second-half strikes from Rhys McCabe and Scott McGill – hours after he completed a loan move from Hearts.
Motherwell had 700 fans in the 2,000 crowd at the Penny Cars Stadium for the first Lanarkshire derby between the teams in 14 years and many of those who stayed to the end vented their anger towards the players.
Alexander said: "First half I thought we were OK without causing too many problems for the opposition but second half we lost way too many physical duels and we lost the game on the competitive side.
"You have to earn the right to win in any game of football, in any sport. You have to earn the right through endeavour, through work rate. We have gymnasiums to build our bodies strong for a reason – so we are competitive."
The result puts both teams on six points ahead of their final fixture. Group F leaders Queen's Park have seven points but have completed their fixtures.
Alexander, whose side host Annan on Saturday, said: "Everyone will understand that tonight was nowhere near good enough and none of us are happy about it, but we are the ones who have the opportunity to change it. We have another game in two days' time to put it right and that's what we have to do."
Airdrie boss Ian Murray said: "I thought we were excellent and I think for the second half we deserved it. It's really important we keep our feet on the ground because we have a huge game on Saturday against Queen of the South."