By Sean Walsh Manchester United goalkeeper Andre Onana expressed his frustration after his side’s 1-1 draw away at Brentford on Saturday night. The Red Devils were second-best for much of the contest in west London but looked to have snatched an improbable win when Mason Mount put them ahead in the 96th minute. However, Kristoffer Ajer came up with an equaliser three minutes later to ensure the hosts took a deserved point. Speaking post-match to MUTV, Onana admitted such a late sucker-punch was difficult to swallow. “I feel sad because we are Manchester United, so it doesn’t matter who you pla…