It was Lendl who invited Pete. You can read more about it in the link below:
https://www.atpworldtour.com/en/news/deuce-us-open-2010-sampras
Shy and impressionable, 18-year-old Pete Sampras arrived at the house of World No. 1 Ivan Lendl in Greenwich, Connecticut, in November 1989. He had replaced high school with tennis' nomadic life in the single-minded pursuit of becoming a great champion when he turned pro in Philadelphia 20 months earlier. As a natural talent, with an attacking style that was so fluent, even artistic, as to make the sport appear easy, his game was in complete contrast to that of Lendl.
Lendl worked for everything. On the court, he dominated his opponents from the baseline until they buckled. Off the court, he lived the American dream, retiring to his 15,000-square-foot house behind six-foot high fencing and protected by two alarm systems. It was at this house Lendl invited Sampras for 10 days, prior to competing at the Nabisco Masters in Madison Square Garden, New York City.
"Ivan wanted to see me play, so he gave me a call and invited me to his house, which was an eye-opener," recalls Sampras. "It was huge. Ivan and his wife, Samantha, made me feel welcome and comfortable.
"He soon had me biking 20 to 25 miles a day. And we spoke about my tennis, how hard you have to work if you want to make it to the top. I learnt a lot about how a top professional trained and how he looked after himself."
Lendl, who will compete for the first time on the ATP Champions Tour at Paris in October, remembers, "He stayed for about 10 days and observed everything. I could tell Pete was a huge talent, but [he] was still young and was still developing his game. Even the serve was still unrefined. I did not predict he would go on and win 14 majors."
Sampras had sampled the disciplined lifestyle and immediately returned to Bradenton, Florida, to re-join his friend Jim Courier at the IMG-Bollettieri Tennis Academy, where he was living, and where he would start to bulk up his muscles and develop his game as an instigator, which he had showcased in beating defending champion Mats Wilander at the US Open.