Introducing Bob's Buddy

TL;DR: What is Bob’s Buddy? Bob’s Buddy is a new feature of the Hearthstone Deck Tracker that helps players better understand how likely they are to win, lose or tie each combat round in Battlegrounds and their relative strength to other players in the lobby.

The outcome of a combat round in Battlegrounds can swing heavily based on just a few attacks. What seemed like an easy victory could turn into a crushing loss off of a single errant ping from a Soul Juggler. Parsing through this randomness to analyze your actual chances and understand your true strength relative to your opponent is no easy feat. That’s where Bob’s Buddy comes in.

Bob’s Buddy takes your and your opponent’s board and simulates upwards of 10,000 combats until we are able to accurately predict it. We then take those results and show how likely you are to win, lose or tie in that combat, as well as how likely you are to have lethal or be eliminated by your opponent. This all usually happens in the blink of an eye.

Take the following board as an example:

Bob’s Buddy would take this board and simulate this combat according to the rules of Battlegrounds. The possible outcomes in this case are:

  • If the friendly player attacks first, the 3/1 Fiendish Servant attacks the Vulgar Homunculus and then the 2/1 Fiendish Servant attacks the Dire Wolf Alpha. Lich King wins. (50% chance)
  • If Lich King attacks first and the 2/1 Fiendish Servant attacks the 3/1 Fiendish Servant, and the Dire Wolf Alpha, now a 5/2, attacks the Vulgar Homunculus. It’s a tie. (25% chance)
  • If Lich King attacks first and the 2/1 Fiendish Servant attacks the 2/2 Dire Wolf Alpha, and then the 3/1 Fiendish Servant attacks the Vulgar Homunculus. Lich King wins. (25% chance)

So the Lich King wins this combat 75% of the time and there’s a tie the other 25%. In the screenshot above, Bob’s Buddy shows 25.2% and 74.8% because Bob’s Buddy runs thousands of simulations to converge on the most reliable estimate. In that screenshot 252 times there was a tie, and 748 times there was a loss.

Now that board was pretty simple, and it’s easy to calculate all the different outcomes. But what about this one?

This board is nowhere near as trivial to predict all the different outcomes. In this instance, the friendly player won the combat and dealt lethal damage to their opponent, even though the likelihood of that happening was fairly low. With the help of Bob’s Buddy, this player would know that they got lucky in this combat, instead of erroneously thinking that their board was stronger than their opponent’s, which could lead to sub-optimal decisions in future turns.

How can I get Bob's Buddy?

Bob’s Buddy is currently in Beta and is available for free to all Hearthstone Deck Tracker users, and can be disabled/enabled and customized directly from the settings panel. If you don’t have Hearthstone Deck Tracker yet, you can download it to access Bob’s Buddy and a host of other Battlegrounds (and classic Hearthstone) features.

If you’re interested in more Battlegrounds statistics, subscribe to Tier7 to learn more about the best Heroes and Compositions, when to tavern up, how to position your minions and much more.


Frequently Asked Questions

Q: How accurate is Bob’s Buddy?

A: Very. By using HSReplay.net’s library of uploaded Battlegrounds games, we have run tens of thousands of combat rounds through Bob’s Buddy and compared the predicted results to the actual results to guarantee that it meets our internal quality thresholds.

This is a graph of Bob’s Buddy’s accuracy. Each point represents a group of hundreds of combat rounds for which Bob’s Buddy had similar predictions. They are grouped according to what percentage of the time Bob’s Buddy predicted they would win; this determines their place on the x-axis. Then we check what percentage of those rounds were actually won in real life. This determines the dot’s placement on the y-axis. If Bob’s Buddy is accurate, then for example, we would expect that 60% of the combat rounds were actually won, for the bucket of combat rounds where Bob’s Buddy predicted a 60% chance to win. As you can see from the resulting chart, that all the dots are very close to the Y = X line, confirming that Bob’s Buddy is indeed accurate.

Q: How do you handle infinite loops?

A: Infinite loops are not possible in Battlegrounds. Ghastcoiler can’t summon itself and Sneed’s Old Shredder can’t summon Ghastcoiler, since it isn’t a Legendary minion. The closest thing to an infinite loop is both players having 0 attack minions or no minions at all, in which case Bob’s Buddy would recognize that as a guaranteed tie.

Q: Does it take into account Akazamzarak’s secrets?

A: It does if you are playing as Akazamzarak, but not if you are playing against it. We will be adding support for this in the future. Currently when you face Akazamzarak, if there are any secrets in play Bob’s Buddy will deactivate and not provide results for that combat round.

Q: Will this help me improve in the game?

A: We hope so. By being aware of how strong/weak your board is compared to your opponents’, you will have a better idea of how the decisions you’ve made so far have impacted your chances of winning combat, and will help you decide when (and if) you should be tiering up. Over time, we hope this helps you develop your intuition about how powerful your warbands are.

Q: Does this give players an unfair advantage?

A: We don’t believe it does. Bob’s Buddy only provides you with information about your combat performance after combat has begun when you can no longer make any gameplay decisions. We do hope that using it over time will help you become a better player!

Q: Is Bob Buddy's available on Mac?

A: Yes! As of October 1st, 2020 Bob's Buddy is also available on Mac.

Q: Does Bob's Buddy work in Spectator Mode?

A: Yes!


Special thanks to Purple, Firebat, and SirSalty, and my personal friends Ben Bunze and Jake Oxendine, who were incredibly helpful and supportive in the early stages of developing Bob's Buddy. Thanks also to all the testers who helped us get it this far.