Tennis - 2017 Nitto ATP Finals at The O2 - Day Two<br />
<br />
Group Pete Sampras Singles: Dominic Thiem (Austria) Vs Grigor Dimitrov (Bulgaria)<br />
<br />
Grigor Dimitrov (Bulgaria) opens himself up to return serve at the O2 Arena <br />
<br />
<br />
COLORSPORT/DANIEL BEARHAM