LONDON, Jan 25 (Reuters) - Aston Villa's unhappy season went from bad to worse when they slumped to a 2-1 defeat at second tier Millwall in the fourth round of the FA Cup on Friday. Darren Bent put Paul Lambert's team in front early on but the Premier League strugglers were then rocked by goals from Danny Shittu (27 minutes) and John Marquis (89). Villa also suffered a shock defeat by fourth tier Bradford City in the semi-finals of the League Cup on Tuesday.