Frightening to the point where that Aug. 2 collision at Fenway Park looked like it might threaten the promising career of Cleveland's young catcher. Now, though, that violent play at the plate is just a memory, and Santana is back at full strength, participating in Spring Training like nothing happened.
Santana is catching bullpen sessions, running through agility drills and taking part in batting practice from both sides of the plate. On Thursday, Santana slid on his surgically repaired left knee, passing the final test in what Acta can only describe now as a miraculous recovery.
"God bless modern medicine, man," Acta said with a smile.
Having Santana back is certainly a blessing for the Tribe.
Prior to having his season prematurely ended in 2010, Santana showed flashes of the star the Tribe believes he can become. After joining the team in June, Santana breathed some life into the middle of Cleveland's lineup, where he figures to be placed once again when Opening Day arrives this year.
"He just flat out made an impact on our lineup," Acta said.
Santana opened last year at Triple-A Columbus and went on to hit .316 with 13 home runs, 51 RBIs and a 1.044 OPS in 57 games before being summoned to The Show. Over 46 games with the Indians, Santana hit at a .260 clip with six homers, 22 RBIs and a .401 on-base percentage.
Acta was quick to note that Santana did the bulk of his damage when the Indians were without top-of-the-lineup hitters Grady Sizemore and Asdrubal Cabrera due to injuries. The Tribe expects to have an improved offense this season, giving the team hope that Santana can be a legitimate run producer.
It is a situation that has Santana excited.
"The team here is very good," said Santana, who turns 25 in April. "We're younger, obviously, but everybody's hungry. I think it's very good."
Santana never thought his knee injury would alter the course of his career.
"No, no, no," he said. "I felt more positive."
The Indians shared that sentiment upon receiving initial reports of the damage Santana suffered in the collision with Kalish.
"It wasn't as serious as it looked," Acta said.
It looked very serious.
On a ball hit into right field at Fenway Park, Kalish sprinted from second base, flying around third and toward home plate. Santana was waiting for a throw from Indians right fielder Shin-Soo Choo and could not see Kalish as the baseball came in.
Santana blocked the plate with his left leg while receiving the throw, and Kalish slid into the catcher with his legs. Amazingly, Santana applied the tag and held tight to the ball throughout the play. Kalish was out, but Santana's season was over.
Santana tore the lateral collateral ligament in his left knee, and Dr. Rick Parker performed surgery to repair the damage on Aug. 6. Aside from a few trips home to the Dominican Republic to see his family, Santana spent this past offseason rehabbing his knee at the Tribe's player development complex in Arizona.
He might not have worried about his long-term future, but Santana is amazed at how fast he was able to recover.
"I'm surprised," he said. "I was here all winter, and the doctor said it's very good, that the knee is very strong. The doctor said he could not believe how strong the knee was right now."
Parker -- also a team doctor for the Cleveland Cavaliers -- made a special trip to Arizona on Feb. 7 to evaluate Santana's progress. After examining the catcher's knee, Parker cleared Santana to begin all baseball activities.
Santana has done so with great enthusiasm.
"It's been impressive to see this guy do whatever he wants to do," Acta said. "The last time I saw him, he was on crutches and down here by himself working out."
The last time Indians fans saw Santana, it was even worse.
The Indians are counting their blessings.
"It's great to see," Indians general manager Chris Antonetti said. "He's on track to just have a regular Spring Training. If you had told us that was going to be the outcome that day when he had that collision in Boston, I'm not sure we would've thought that would've been the case.
"But he's on track to have a normal spring. Obviously, he's a very important guy for our team and our lineup."