Oklahoma City’s big man needs to be prepared for a big role in the second round.  The Thunder are gearing up, as their second-round matchup against the Los Angeles Lakers is set to start on Tuesday night. OKC is coming into this series after a dominant first round, sweeping Phoenix to open up the postseason. L.A., on the other hand, struggled in the back end of its first-round series, but was able to finish the series in six games.  Oklahoma City is looking to display dominance once again in its upcoming series and will need the help of a certain OKC big to do so.  Chet Holmgren came alive for the Thunder in the first round and will have to do so again starting Tuesday. Holmgren averaged 17.1 points per game against Phoenix and added 8.5 rebounds and two blocks per game to round out his round-one resume.…