A player who doesn't buckle under pressure, could be said to deliver the goods. I would also describe such a player as being ruthless and consistent.

There is an Italian football (soccer) player called Mario Balotelli who played for Manchester City until 2012, his track record in penalty taking is phenomenal. He missed his first penalty in his professional career on 22 September 2013, in the previous 26 attempts, Balotelli had always scored.

First minute or last, big game or small, game on the line or dead and buried, Mario just does not miss. (...) Players who are psychologically prepared have a greater chance of succeeding in a penalty situation," Dr. Cohen continues. "Coaches know this and even get players to practice in front of crowds so they can experience the pressure. However, the pressure is so intense that it is difficult even for the most experienced players to be absolutely consistent in these situations

A reputable baseball coach has this to say ¹

The difference in playing a game in the backyard, home park, or in Omaha at the College World Series is not in the playing field but in the mind of the player...this is why a consistent approach to every game is the key! (...)

To place any more importance on one game is to get out of the consistent preparation and consistent performance so vitally needed to be a consistent athlete who can perform properly under pressure

EDIT
A slang term but it fits. Clutch
to perform under pressure In the last few seconds of a close game, only a player with clutch can lead the team to victory. (Derived from the clutch mechanism in a manual car, where perfect timing can mean the difference between a launch and a stall)

A player who doesn't buckle under pressure, could be said to deliver the goods. And I would also describe such a player as being ruthless and consistent.

However, a slang term which fits the Op's request is clutch:
to perform under pressure In the last few seconds of a close game, only a player with clutch can lead the team to victory. (Derived from the clutch mechanism in a manual car, where perfect timing can mean the difference between a launch and a stall)

A reputable baseball coach has this to say: ¹

If a hitter is averaging .333 and gets a hit one time in three clutch situations, he is performing well in the clutch... normal performance under pressure is the goal, not super performance.

All too often an athlete gets the reputation as a "great clutch player" because of one or two performances that got a lot of media attention, but the truth of the matter is most of the time a "great clutch performer" is one who performs normally under pressure.

A player who doesn't buckle under pressure, could be said to deliver the goods. I would also describe such a player as being ruthless and consistent.

There is an Italian football (soccer) player called Mario Balotelli who played for Manchester City until 2012, his track record in penalty taking is phenomenal. He missed his first penalty in his professional career on 22 September 2013, in the previous 26 attempts, Balotelli had always scored.

First minute or last, big game or small, game on the line or dead and buried, Mario just does not miss. (...) Players who are psychologically prepared have a greater chance of succeeding in a penalty situation," Dr. Cohen continues. "Coaches know this and even get players to practice in front of crowds so they can experience the pressure. However, the pressure is so intense that it is difficult even for the most experienced players to be absolutely consistent in these situations

A reputable baseball coach has this to say ¹

The difference in playing a game in the backyard, home park, or in Omaha at the College World Series is not in the playing field but in the mind of the player...this is why a consistent approach to every game is the key! (...)

To place any more importance on one game is to get out of the consistent preparation and consistent performance so vitally needed to be a consistent athlete who can perform properly under pressure

A player who doesn't buckle under pressure, could be said to deliver the goods. I would also describe such a player as being ruthless and consistent.

There is an Italian football (soccer) player called Mario Balotelli who played for Manchester City until 2012, his track record in penalty taking is phenomenal. He missed his first penalty in his professional career on 22 September 2013, in the previous 26 attempts, Balotelli had always scored.

First minute or last, big game or small, game on the line or dead and buried, Mario just does not miss. (...) Players who are psychologically prepared have a greater chance of succeeding in a penalty situation," Dr. Cohen continues. "Coaches know this and even get players to practice in front of crowds so they can experience the pressure. However, the pressure is so intense that it is difficult even for the most experienced players to be absolutely consistent in these situations

A reputable baseball coach has this to say ¹

The difference in playing a game in the backyard, home park, or in Omaha at the College World Series is not in the playing field but in the mind of the player...this is why a consistent approach to every game is the key! (...)

To place any more importance on one game is to get out of the consistent preparation and consistent performance so vitally needed to be a consistent athlete who can perform properly under pressure

EDIT
A slang term but it fits. Clutch
to perform under pressure In the last few seconds of a close game, only a player with clutch can lead the team to victory. (Derived from the clutch mechanism in a manual car, where perfect timing can mean the difference between a launch and a stall)