Mark Trumbo is a great base runner when he homers.

Duh.

Even the great Hank Aaron made out as a base runner when a teammate "homered". It actually does happen on very, very rare occasions.

Tuesday, May 26, 1959, 8:00PM, County Stadium
Attendance: 19,194, Time of Game: 2:54
Braves 1, Pirates 0

Pitching	IP	H	R	ER	BB	SO	HR	ERA	BF	GSc	IR	IS	WPA	aLI	RE24
Harvey Haddix, L (4-3)	12.2	1	1	0	1	8	0	2.16	40	107			0.660	1.38	4.5
Team Totals	12.2	1	1	0	1	8	0	0.00	40	107			0.660	1.38	4.5

Provided by Baseball-Reference.com: View Original Table
Generated 1/28/2017.

Pitching	IP	H	R	ER	BB	SO	HR	ERA	BF	GSc	IR	IS	WPA	aLI	RE24
Lew Burdette, W (8-2)	13	12	0	0	0	2	0	3.32	47	85			1.159	1.61	5.8
Team Totals	13	12	0	0	0	2	0	0.00	47	85			1.159	1.61	5.8

Provided by Baseball-Reference.com: View Original Table
Generated 1/28/2017.

This is the famous game in which Pirate starter Harvey Haddix pitched 12 perfect innings. But here's the largely forgotten oddity involving Aaron in the bottom of the 13th inning.

Felix Mantilla reached on an error.
Eddie Mathews made a sacrifice bunt to move Mantilla to second.
Haddix intentionally walked Aaron.
Joe Adcock "homered".

Baseball-Reference.com:
Double to CF (Deep CF-RF); Mantilla Scores/unER; Aaron to 3B; Adcock out at 2B/SS; Joe Adcock hit the ball into the right center stands for a homerun, but was declared out for passing Henry Aaron between 2B and 3B; Aaron thought the ball had landed inside the fence; 1B Umpire Frank Dascoli ruled the final score was 2 to 0 but was overruled by NL President Warren Giles who said that since it was only a double, then only one run was needed to win the game;
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Which brings us to base running as a skill. WAR definitions from baseball-reference.com:

WAR -- Wins Above Replacement
A single number that presents the number of wins the player added
to the team above what a replacement player (think AAA or AAAA) would add.
Scale for a single-season: 8+ MVP Quality, 5+ All-Star Quality, 2+ Starter,
0-2 Reserve, < 0 Replacement Level
Developed by Sean Smith of BaseballProjection.com

oWAR -- Offensive Wins Above Replacement (everything but Fielding)
The same statistic as Wins Above Replacement for Position
Players (WAR), but with the fielding value excluded.
oWAR + dWAR does not equal WAR.
Adding would count positions twice.
Contains the factor for batting stats, baserunning, a positional adjustment, and the replacement player adjustment.
Factors developed by Sean Smith of BaseballProjection.com
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When Hank Aaron or Mark Trumbo hits a home run he almost never makes out; nor do any teammates who are on base. Almost never.

So why aren't those plate appearances considered in evaluating the base running skill of a player? That skill is extended to runners on base. Players who are otherwise considered slow and/or bad base runners become, not just neutral base runners, but GREAT base runners, who will score almost all the time. You cannot say that about Rickey Henderson or Tim Raines when they attempted to steal a base.

Mark Trumbo hit the most home runs in 2016: 47 for the Orioles. He then became a free agent and languished as teams ignored him. Finally, the Orioles signed Trumbo. Maybe they realized his hidden skill.