World number seven David Goffin levelled the tie with an upset straight-sets win over fourth ranked Alexander Zverev, but Zverev and Kerber then claimed the deciding mixed doubles. Kerber was delighted to start 2018 with a victory, having battled a dramatic slump in form last year.
She started 2017 ranked world number one but by the end of the season the dual Grand Slam winner had slipped to 21. Kerber was fully tested by Mertens, whose ranking went the other way in 2017 as she climbed from 120 to 36. The pair traded service breaks and winners, but it was Kerber who produced when it mattered to win 7-6 (8/6), 7-6 (7/1) in one hour and 56 minutes. Kerber, who won her maiden Grand Slam title at the Australian Open in 2016, said it was a promising start to her preparation for Melbourne.