BOSTON — The return of Marcus Smart to the Boston Celtics lineup remains unclear. 

The eye infection that has kept Smart out of Boston's last three games has not improved. 

Actually, it has gotten worse. 

"It's in both eyes now," said Celtics head coach Brad Stevens. "So he's struggling a little bit."

The same could be said for Boston's defense in his absence. 

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In the last three games, Boston has allowed an average of 108.3 points per game — nearly four more points per game above their season average.

And while Boston's defensive rating of 104.1 ranks eighth in the NBA, the last three Smart-less games for Boston have seen that number slip to 112.5, which ranks 22nd in the league over that span.

While it's certainly disappointing that Smart is still dealing with an eye infection, Stevens gets a sense that it won't be that much longer before Smart is back on the floor after conversations Stevens had with the team's medical staff. 

"This particular type of infection can be 7-10 days," Stevens recalls being told. "So we're at (day) seven now."

That likely means Smart will be a game-time decision as far as whether he will play near his Texas roots later this week when Boston hits the road to face off against Dallas on Wednesday. 

Don't miss NBC Sports Boston's coverage of Celtics-Mavericks, which tips off Wednesday at 8:30 p.m. with Celtics Pregame Live, and then Kyle Draper, Brian Scalabrine and Kendrick Perkins have the call at 9:30 p.m. You can also stream the game on the MyTeams App.