Tottenham Hotspur on Tuesday suffered and embarrassing League Cup third-round (Carabao Cup) defeat on penalties at fourth-tier Colchester.
The North London club was held to a 0-0 draw in normal time before losing 4-3 on penalties.
Arsenal, on the other hand, demolished Nottingham Forest 5-0 to boost their confidence.
Brazilian striker Gabriel Martinelli scored his first goals in English football and Rob Holding also enjoyed a dream return from injury.
Martinelli, making his first Gunners start, claimed the first-half opener before completing the scoring in stoppage time.
Defender Holding, out for more than nine months with a serious knee problem, headed home the second goal in the final 19 minutes, with Joe Willock (3) and Reiss Nelson (4) also on target.
FULL EFL CUP RESULTS:
Arsenal 5-0 Nottingham Forest
Colchester 0-0 Tottenham (Colchester win 4-3 on penalties)
Luton 0-4 Leicester
Portsmouth 0-4 Southampton
Preston 0-3 Manchester City
Sheffield Wednesday 0-2 Everton
Watford 2-1 Swansea