Shares of gourmet burger chain Red Robin (NASDAQ:RRGB) were slammed earlier this month when the company reported preliminary second-quarter results in an effort to be timely and transparent about a period that was "significantly" worse than expected, according to Red Robin CEO Denny Marie Post. Shares slid about 20% as adjusted earnings per share came in well below the company's guidance range.

The preliminary second-quarter update, which included figures that are subject to quarter-end closing adjustments, gave investors some insight into the period. But there are still items for investors to watch when Red Robin reports its official second-quarter results. Questions remain about why the company didn't execute up to par, when management believes it can turn around its negative customer traffic trend, and more.

Here are three topics investors will want to check on when Red Robin reports its second-quarter results.

The outside of a Red Robin Gourmet Burgers restaurant at night.

Image source: Red Robin Gourmet Burgers.

What factors, exactly, led to Red Robin's significant underperformance?

Red Robin's poor second-quarter performance wasn't just weak -- it was meaningfully worse what management was guiding for.

Red Robin had forecast second-quarter earnings per share to be between $0.55 and $0.77. Actual EPS, however, came in at $0.14, or $0.46 when excluding asset impairment, reorganization, and other charges. Analysts were even fooled. The consensus earnings-per-share forecast from analysts for the quarter was $0.65.

Second-quarter revenue of $315 million was also well below a consensus forecast for $324 million.

While it was good to see management refraining from making excuses, the preliminary update was lacking details to explain exactly why results were so far from expectations. Post said:

While we remain confident in the strategy that we have in place to address the shifts going on within casual dining, we simply didn't execute as well as we should have. We have opportunities to improve our service execution, which has been impacted by the growing complexity of the multiple revenue streams within our four walls. We must also refresh our marketing message and move quickly on the digital guest experience.

Investors should look for a more specific breakdown of what went wrong.

When can Red Robin turn things around?

Following already-somber 0.1% year-over-year growth in comparable restaurant guest counts in Q1, the restaurant's customer traffic trend worsened in Q2. Comparable guest count decreased 0.7% year over year during the quarter.

"We continue to make progress on driving off-premise traffic growth and differentiation through everyday affordability," said Post. "However, we have yet to see the needed lift in dine-in traffic to offset the lower check average associated with the higher mix of our Tavern Double Menu."

Investors should look for answers as to when this metric is expected to turn positive.

Can Red Robin maintain its revised guidance?

For Red Robin to begin earning back investors' confidence, it's going to need to begin meeting or exceeding its guidance.

Management was initially forecasting 2018 earnings per share between $2.40 and $2.80. But after releasing its preliminary second-quarter results, Red Robin said it expects full-year EPS between $1.80 and $2.20. In addition, management now expects comparable restaurant revenue to decline 1% to 2% year over year in 2018. This is down from a previous forecast for comparable restaurant sales growth between 50 to 150 basis points.

With its second-quarter results being released nearly three weeks after its preliminary results, management will have better vision into Q3 and the remainder of the year. Investors should look for Red Robin to affirm that its current guidance is realistic, if not conservative.