Graeme McDowell is two shots off the lead after the opening day's action at the Hero World Challenge in Florida.

The Ulsterman carded a bogey on the 18th to card a 4-under par 68.

21-year-old American Jordan Spieth leads the field on 6-under par after 13 holes of his round.

But tournament host Tiger Woods trails the field, struggling on 5-over par in his first competition since last August.

The 14-time Major winner carded five bogies, including a double at the eighth.