Chelsea's Cole Palmer squandered a hat-trick of chances as Hayden Hackney handed Championship Middlesbrough a crucial first-leg lead in their Carabao Cup semi-final.The England international, who had earlier been denied by Boro keeper Tom Glover, passed up three opportunities either side of Hackney's 37th-minute strike, which ensured Michael Carrick's men will head for Stamford Bridge in a fortnight's time with a 1-0 lead.